Methods of driving light sources in a near-eye display

ABSTRACT

A method including determining a maximum luminance location of a display based on a field of view of an eye of a user of the display, and driving a plurality of light sources in the display based on locations of the plurality of light sources with respect to the maximum luminance location of the display. The plurality of light sources is controlled to have different luminance levels in different display zones corresponding to different zones on the retina of the eye of the user. In some examples, the display zones of the display system that have higher luminance levels can be dynamically changed based on the field of view or the gaze direction of the eye of the user.

BACKGROUND

An artificial reality system, such as a head-mounted display (HMD) orheads-up display (HUD) system, generally includes a near-eye displaysystem in the form of a headset or a pair of glasses and is configuredto present content to a user via an electronic or optic display within,for example, about 10-20 mm in front of the user's eyes. The near-eyedisplay system may display virtual objects or combine images of realobjects with virtual objects, as in virtual reality (VR), augmentedreality (AR), or mixed reality (MR) applications. For example, in an ARsystem, a user may view both images of virtual objects (e.g.,computer-generated images (CGIs)) and the surrounding environment by,for example, seeing through transparent display glasses or lenses (oftenreferred to as optical see-through) or viewing displayed images of thesurrounding environment captured by a camera (often referred to as videosee-through). The display system generally includes one or more lightsources that are driven to output light at various luminance levels.

SUMMARY

This disclosure relates generally to display system. According tocertain embodiments, a method may include determining a maximumluminance location of a display based on a field of view of an eye of auser of the display, and driving a plurality of light sources in thedisplay based on locations of the plurality of light sources withrespect to the maximum luminance location of the display. Each lightsource of the plurality of light sources may be driven by a respectivedrive circuit to emit light. For a first light source and a second lightsource in the plurality of light sources and associated with a sameinput display value, the first light source may be driven to emit lightat a first luminance level higher than a second luminance level of thesecond light source that is farther from the maximum luminance locationthan the first light source.

In some embodiments of the method, the maximum luminance location is ata center of the field of view of the eye of the user or within a fieldof view of a fovea of the eye of the user. Determining the maximumluminance location of the display may include tracking a position of theeye of the user with respect to the display. Driving the plurality oflight sources may include driving the first light source based on theinput display value and a first relationship between input displayvalues and luminance levels for light sources in a first display zone ofthe display, and driving the second light source based on the inputdisplay value and a second relationship between input display values andluminance levels for light sources in a second display zone of thedisplay. The luminance levels for the light sources in the first displayzone may be characterized by a first range larger than a second range ofthe luminance levels for the light sources in the second display zone.In some embodiments, the difference between the first luminance leveland the second luminance level may be less than a threshold value. Eachlight source of the plurality of light sources may include, for example,an organic light emitting diode (OLED) or a micro-light emitting diode(micro-LED).

According to certain embodiments, a system may include a displayincluding a plurality of light sources, and a display controllerincluding a respective drive circuit for each of the plurality of lightsources. The display controller may be configured to select a maximumluminance location of the display based on a field of view of an eye ofa user of the system, and drive the plurality of light sources based onlocations of the plurality of light sources with respect to the maximumluminance location of the display. For a first light source and a secondlight source in the plurality of light sources and associated with asame input display value, the display controller is configured to drivethe first light source to emit light at a first luminance level higherthan a second luminance level of the second light source that is fartherfrom the maximum luminance location than the first light source.

In some embodiments of the system, the maximum luminance location may bein a field of view of a fovea of the eye of the user or a center of thefield of view of the eye of the user. In some embodiments, the maximumluminance location may be at a center of the display. In someembodiments, each light source of the plurality of light sources mayinclude an organic light emitting diode (OLED) or a micro-light emittingdiode (micro-LED).

In some embodiments, the display controller may be configured to drivethe first light source based on the input display value and a firstrelationship between input display values and luminance levels for lightsources in a first display zone of the display, and drive the secondlight source based on the input display value and a second relationshipbetween input display values and luminance levels for light sources in asecond display zone of the display, where the luminance levels for thelight sources in the first display zone are characterized by a firstrange lager than a second range of the luminance levels for the lightsources in the second display zone. In some embodiments, a differencebetween the first luminance level and the second luminance level may beless than a threshold value that is noticeable by the eye of the user.In some embodiments, the display controller may be configured to driveeach light source of the plurality of light sources based upon adistance from the light source to the maximum luminance location.

In some embodiments, the system may include an eye-tracking subsystemconfigured to track a position of the eye of the user with respect tothe display and determine a gaze direction or the field of view of theeye of the user.

According to certain embodiments, a non-transitory machine-readablestorage medium may include instructions stored thereon. Theinstructions, when executed by one or more processors, may cause the oneor more processors to perform operations including determining a maximumluminance location of a display based on a field of view of an eye of auser of the display, and driving a plurality of light sources in thedisplay based on locations of the plurality of light sources withrespect to the maximum luminance location of the display. Each lightsource of the plurality of light sources may be driven by a respectivedrive circuit to emit light. For a first light source and a second lightsource in the plurality of light sources and associated with a sameinput display value, the first light source may be driven to emit lightat a first luminance level higher than a second luminance level of thesecond light source that is farther from the maximum luminance locationthan the first light source.

In some embodiments of the non-transitory machine-readable storagemedium, the maximum luminance location may be at a center of the fieldof view of the eye of the user. In some embodiments, determining themaximum luminance location of the display may include tracking aposition of the eye of the user with respect to the display. In someembodiments, driving the plurality of light sources may include drivingthe first light source based on the input display value and a firstrelationship between input display values and luminance levels for lightsources in a first display zone of the display, and driving the secondlight source based on the input display value and a second relationshipbetween input display values and luminance levels for light sources in asecond display zone of the display. The luminance levels for the lightsources in the first display zone may be characterized by a first rangelarger than a second range of the luminance levels for the light sourcesin the second display zone.

This summary is neither intended to identify key or essential featuresof the claimed subject matter, nor is it intended to be used inisolation to determine the scope of the claimed subject matter. Thesubject matter should be understood by reference to appropriate portionsof the entire specification of this disclosure, any or all drawings, andeach claim. The foregoing, together with other features and examples,will be described in more detail below in the following specification,claims, and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Illustrative embodiments are described in detail below with reference tothe following figures.

FIG. 1 is a simplified block diagram of an example of an artificialreality system environment including a near-eye display according tocertain embodiments.

FIG. 2 is a perspective view of an example of a near-eye display in theform of a head-mounted display (HMD) device for implementing some of theexamples disclosed herein.

FIG. 3 is a perspective view of an example of a near-eye display in theform of a pair of glasses for implementing some of the examplesdisclosed herein.

FIG. 4 illustrates an example of an optical see-through augmentedreality system including a waveguide display according to certainembodiments.

FIG. 5A illustrates an example of a near-eye display device including awaveguide display according to certain embodiments.

FIG. 5B illustrates an example of a near-eye display device including awaveguide display according to certain embodiments.

FIG. 6 illustrates an example of an image source assembly in anaugmented reality system according to certain embodiments.

FIG. 7 is a cross-sectional view of an example of a near-eye displaysystem according to certain embodiments.

FIG. 8 illustrates light reflections and scattering by an eye during eyetracking.

FIG. 9 is a simplified flowchart illustrating an example of a method fortracking the eye of a user of a near-eye display system according tocertain embodiments.

FIG. 10A illustrates an example of an image of a user's eye captured bya camera according to certain embodiments.

FIG. 10B illustrates an example of an identified iris region, an exampleof an identified pupil region, and examples of glint regions identifiedin an image of the user's eye according to certain embodiments.

FIG. 11 is a simplified block diagram of an example of a controller fora near-eye display system according to certain embodiments.

FIGS. 12A-12D illustrate examples of methods for driving light sourcesin a display system according to certain embodiments.

FIG. 13 is a simplified flowchart illustrating an example of a methodfor driving light sources in a display system according to certainembodiments.

FIG. 14 is a simplified block diagram of an electronic system of anexample of a near-eye display according to certain embodiments.

The figures depict embodiments of the present disclosure for purposes ofillustration only. One skilled in the art will readily recognize fromthe following description that alternative embodiments of the structuresand methods illustrated may be employed without departing from theprinciples, or benefits touted, of this disclosure.

In the appended figures, similar components and/or features may have thesame reference label. Further, various components of the same type maybe distinguished by following the reference label by a dash and a secondlabel that distinguishes among the similar components. If only the firstreference label is used in the specification, the description isapplicable to any one of the similar components having the same firstreference label irrespective of the second reference label.

DETAILED DESCRIPTION

Techniques disclosed herein relate generally to display systems. Morespecifically, and without limitation, disclosed herein are techniquesfor controlling the luminance levels of light sources in displaysystems. Techniques disclosed herein can improve the power efficiency ofthe display system, while maintaining the user experience. Variousinventive embodiments are described herein, including devices, systems,methods, materials, and the like.

For a portable display system, such as a near-eye display system, it maybe desirable that the display system has a lower power consumption andthus a longer battery life and/or a longer battery lifespan. It is alsodesirable that the display system has a high luminance level or lightintensity for a good user experience. Therefore, a display system thatcan both achieve a high luminance and have a low power consumption maybe needed.

Human eyes are generally less sensitive to light from larger viewingangles with respect to the foveal axis. The sensitivity may peak at thefoveal zone and quickly decrease outside of the foveal zone. Forexample, the number of receptors may decrease from approximately 155,000receptors per square millimeter near the fovea to fewer than 10,000receptors per square millimeter at a region corresponding to a viewangle of 10° or greater with respect to the foveal axis. Therefore,portions of a display panel that are farther away from the center of thefield of view of a user may not be very noticeable to the user's eyeeven if these portions of the display panel have high luminance levelsor high light intensities.

According to certain embodiments, light sources in a display may becontrolled to have different luminance levels in different display zonescorresponding to different zones on the retina of a user's eye. Forexample, the light sources in a display zone that may be imaged onto azone of the retina including the fovea may have higher luminance levels(or brightness), while light sources in a display zone that may beimaged onto a peripheral zone of the retina may have lower luminancelevels. In one example, in an active matrix organic light emitting diode(AMOLED) display panel that includes a plurality of organic lightemitting diodes (OLEDs), each OLED may be driven individually by a drivecircuit to emit light at a desired luminance level. Each OLED may emitat a different respective luminance level, or a subset of OLEDs within asame display zone may emit at the same luminance level. By reducing theluminance of the OLEDs in peripheral zones, the power used by thedisplay panel may be reduced, with minimum or no impact on userexperience. In some examples, the reduction in power may be betweenabout 5% and about 10%, between about 10% and about 20%, between about20% and about 30%, or between about 30% and about 40%. In anotherexample, a micro-LED array-based display system may include individuallycontrolled micro-LEDs, where the micro-LEDs at different regions of themicro-LED array may be controlled to emit at different luminance levels.

In addition, the display zones of the display system that have higherluminance levels may be dynamically changed based on the field of view(or the gaze direction) of the user's eye. For example, an eye-trackingsubsystem of the display system may track the movement of the user's eyeto determine a center of the field of view (or the gaze direction) ofthe user's eye. The control and driving circuits may then control thelight sources at the center of the field of view to emit at highluminance levels, and control the light sources at other display zonesto emit at different lower luminance levels based on the locations ofthe display zones with respect to the center of the field of view.

As used herein, the term “organic light emitting diode” or “OLED” refersto a light emitting diode having an emissive electroluminescent layerthat includes an organic compound that emits light in response to anelectric current. The emissive layer may be arranged between an anodeand a cathode. The organic compound may include small molecules orpolymers.

As used herein, the term “active matrix organic light emitting diode” or“AMOLED” display refers to a display that uses a thin-film transistorbackplane to directly control each individual pixel. An AMOLED displaydoes not use a backlight, because each individual OLED is self-emissive.The amount of luminance provided by each OLED depends on the currentprovided to the OLED.

As used herein, the term “micro-LED” or “μLED” refers to an LED that hasa chip where a linear dimension of the chip is less than about 200 μm,such as less than 100 μm, less than 50 μm, less than 20 μm, less than 10μm, or smaller. For example, the linear dimension of a micro-LED may beas small as 6 μm, 5 μm, 4 μm, 2 μm, or smaller. Some micro-LEDs may havea linear dimension (e.g., length or diameter) comparable to the minoritycarrier diffusion length. However, the disclosure herein is not limitedto micro-LEDs, and may also be applied to mini-LEDs and large LEDs.

As used herein, the term “luminance” refers generally to a photometricmeasure of the luminous intensity per unit area of light travelling in acertain direction. Luminance describes the amount of light that isemitted from, passing through, or reflected from an area and fallswithin a certain solid angle. The luminance level indicates how muchluminous power could be detected by a sensor (e.g., the human eye)looking at a surface from a certain angle of view. Luminance may be anindicator of how bright a surface may appear. The international standardunit for luminance is candela per square meter (cd/m²). Luminance isused in the video industry to characterize the brightness of displays.The term “brightness” refers generally to the perception elicited by theluminance of an object. A given target luminance may elicit differentperceptions of brightness in different contexts. In an RGB color space,brightness can be determined based on the red, green, and blue colorcoordinates

In the following description, for the purposes of explanation, specificdetails are set forth in order to provide a thorough understanding ofexamples of the disclosure. However, it will be apparent that variousexamples may be practiced without these specific details. For example,devices, systems, structures, assemblies, methods, and other componentsmay be shown as components in block diagram form in order not to obscurethe examples in unnecessary detail. In other instances, well-knowndevices, processes, systems, structures, and techniques may be shownwithout necessary detail in order to avoid obscuring the examples. Thefigures and description are not intended to be restrictive. The termsand expressions that have been employed in this disclosure are used asterms of description and not of limitation, and there is no intention inthe use of such terms and expressions of excluding any equivalents ofthe features shown and described or portions thereof. The word “example”is used herein to mean “serving as an example, instance, orillustration.” Any embodiment or design described herein as “example” isnot necessarily to be construed as preferred or advantageous over otherembodiments or designs.

FIG. 1 is a simplified block diagram of an example of an artificialreality system environment 100 including a near-eye display 120 inaccordance with certain embodiments. Artificial reality systemenvironment 100 shown in FIG. 1 may include near-eye display 120, anoptional external imaging device 150, and an optional input/outputinterface 140, each of which may be coupled to an optional console 110.While FIG. 1 shows an example of artificial reality system environment100 including one near-eye display 120, one external imaging device 150,and one input/output interface 140, any number of these components maybe included in artificial reality system environment 100, or any of thecomponents may be omitted. For example, there may be multiple near-eyedisplays 120 monitored by one or more external imaging devices 150 incommunication with console 110. In some configurations, artificialreality system environment 100 may not include external imaging device150, optional input/output interface 140, and optional console 110. Inalternative configurations, different or additional components may beincluded in artificial reality system environment 100.

Near-eye display 120 may be a head-mounted display that presents contentto a user. Examples of content presented by near-eye display 120 includeone or more of images, videos, audio, or any combination thereof. Insome embodiments, audio may be presented via an external device (e.g.,speakers and/or headphones) that receives audio information fromnear-eye display 120, console 110, or both, and presents audio databased on the audio information. Near-eye display 120 may include one ormore rigid bodies, which may be rigidly or non-rigidly coupled to eachother. A rigid coupling between rigid bodies may cause the coupled rigidbodies to act as a single rigid entity. A non-rigid coupling betweenrigid bodies may allow the rigid bodies to move relative to each other.In various embodiments, near-eye display 120 may be implemented in anysuitable form-factor, including a pair of glasses. Some embodiments ofnear-eye display 120 are further described below with respect to FIGS. 2and 3. Additionally, in various embodiments, the functionality describedherein may be used in a headset that combines images of an environmentexternal to near-eye display 120 and artificial reality content (e.g.,computer-generated images). Therefore, near-eye display 120 may augmentimages of a physical, real-world environment external to near-eyedisplay 120 with generated content (e.g., images, video, sound, etc.) topresent an augmented reality to a user.

In various embodiments, near-eye display 120 may include one or more ofdisplay electronics 122, display optics 124, and an eye-tracking unit130. In some embodiments, near-eye display 120 may also include one ormore locators 126, one or more position sensors 128, and an inertialmeasurement unit (IMU) 132. Near-eye display 120 may omit any ofeye-tracking unit 130, locators 126, position sensors 128, and IMU 132,or include additional elements in various embodiments. Additionally, insome embodiments, near-eye display 120 may include elements combiningthe function of various elements described in conjunction with FIG. 1.

Display electronics 122 may display or facilitate the display of imagesto the user according to data received from, for example, console 110.In various embodiments, display electronics 122 may include one or moredisplay panels, such as a liquid crystal display (LCD), an organic lightemitting diode (OLED) display, an inorganic light emitting diode (ILED)display, a micro light emitting diode (μLED) display, an active-matrixOLED display (AMOLED), a transparent OLED display (TOLED), or some otherdisplay. For example, in one implementation of near-eye display 120,display electronics 122 may include a front TOLED panel, a rear displaypanel, and an optical component (e.g., an attenuator, polarizer, ordiffractive or spectral film) between the front and rear display panels.Display electronics 122 may include pixels to emit light of apredominant color such as red, green, blue, white, or yellow. In someimplementations, display electronics 122 may display a three-dimensional(3D) image through stereoscopic effects produced by two-dimensionalpanels to create a subjective perception of image depth. For example,display electronics 122 may include a left display and a right displaypositioned in front of a user's left eye and right eye, respectively.The left and right displays may present copies of an image shiftedhorizontally relative to each other to create a stereoscopic effect(i.e., a perception of image depth by a user viewing the image).

In certain embodiments, display optics 124 may display image contentoptically (e.g., using optical waveguides and couplers) or magnify imagelight received from display electronics 122, correct optical errorsassociated with the image light, and present the corrected image lightto a user of near-eye display 120. In various embodiments, displayoptics 124 may include one or more optical elements, such as, forexample, a substrate, optical waveguides, an aperture, a Fresnel lens, aconvex lens, a concave lens, a filter, input/output couplers, or anyother suitable optical elements that may affect image light emitted fromdisplay electronics 122. Display optics 124 may include a combination ofdifferent optical elements as well as mechanical couplings to maintainrelative spacing and orientation of the optical elements in thecombination. One or more optical elements in display optics 124 may havean optical coating, such as an anti-reflective coating, a reflectivecoating, a filtering coating, or a combination of different opticalcoatings.

Magnification of the image light by display optics 124 may allow displayelectronics 122 to be physically smaller, weigh less, and consume lesspower than larger displays. Additionally, magnification may increase afield of view of the displayed content. The amount of magnification ofimage light by display optics 124 may be changed by adjusting, adding,or removing optical elements from display optics 124. In someembodiments, display optics 124 may project displayed images to one ormore image planes that may be further away from the user's eyes thannear-eye display 120.

Display optics 124 may also be designed to correct one or more types ofoptical errors, such as two-dimensional optical errors,three-dimensional optical errors, or any combination thereof.Two-dimensional errors may include optical aberrations that occur in twodimensions. Example types of two-dimensional errors may include barreldistortion, pincushion distortion, longitudinal chromatic aberration,and transverse chromatic aberration. Three-dimensional errors mayinclude optical errors that occur in three dimensions. Example types ofthree-dimensional errors may include spherical aberration, comaticaberration, field curvature, and astigmatism.

Locators 126 may be objects located in specific positions on near-eyedisplay 120 relative to one another and relative to a reference point onnear-eye display 120. In some implementations, console 110 may identifylocators 126 in images captured by external imaging device 150 todetermine the artificial reality headset's position, orientation, orboth. A locator 126 may be an LED, a corner cube reflector, a reflectivemarker, a type of light source that contrasts with an environment inwhich near-eye display 120 operates, or any combination thereof. Inembodiments where locators 126 are active components (e.g., LEDs orother types of light emitting devices), locators 126 may emit light inthe visible band (e.g., about 380 nm to 750 nm), in the infrared (IR)band (e.g., about 750 nm to 1 mm), in the ultraviolet band (e.g., about10 nm to about 380 nm), in another portion of the electromagneticspectrum, or in any combination of portions of the electromagneticspectrum.

External imaging device 150 may include one or more cameras, one or morevideo cameras, any other device capable of capturing images includingone or more of locators 126, or any combination thereof. Additionally,external imaging device 150 may include one or more filters (e.g., toincrease signal to noise ratio). External imaging device 150 may beconfigured to detect light emitted or reflected from locators 126 in afield of view of external imaging device 150. In embodiments wherelocators 126 include passive elements (e.g., retroreflectors), externalimaging device 150 may include a light source that illuminates some orall of locators 126, which may retro-reflect the light to the lightsource in external imaging device 150. Slow calibration data may becommunicated from external imaging device 150 to console 110, andexternal imaging device 150 may receive one or more calibrationparameters from console 110 to adjust one or more imaging parameters(e.g., focal length, focus, frame rate, sensor temperature, shutterspeed, aperture, etc.).

Position sensors 128 may generate one or more measurement signals inresponse to motion of near-eye display 120. Examples of position sensors128 may include accelerometers, gyroscopes, magnetometers, othermotion-detecting or error-correcting sensors, or any combinationthereof. For example, in some embodiments, position sensors 128 mayinclude multiple accelerometers to measure translational motion (e.g.,forward/back, up/down, or left/right) and multiple gyroscopes to measurerotational motion (e.g., pitch, yaw, or roll). In some embodiments,various position sensors may be oriented orthogonally to each other.

IMU 132 may be an electronic device that generates fast calibration databased on measurement signals received from one or more of positionsensors 128. Position sensors 128 may be located external to IMU 132,internal to IMU 132, or any combination thereof. Based on the one ormore measurement signals from one or more position sensors 128, IMU 132may generate fast calibration data indicating an estimated position ofnear-eye display 120 relative to an initial position of near-eye display120. For example, IMU 132 may integrate measurement signals receivedfrom accelerometers over time to estimate a velocity vector andintegrate the velocity vector over time to determine an estimatedposition of a reference point on near-eye display 120. Alternatively,IMU 132 may provide the sampled measurement signals to console 110,which may determine the fast calibration data. While the reference pointmay generally be defined as a point in space, in various embodiments,the reference point may also be defined as a point within near-eyedisplay 120 (e.g., a center of IMU 132).

Eye-tracking unit 130 may include one or more eye-tracking systems. Eyetracking may refer to determining an eye's position, includingorientation and location of the eye, relative to near-eye display 120.An eye-tracking system may include an imaging system to image one ormore eyes and may optionally include a light emitter, which may generatelight that is directed to an eye such that light reflected by the eyemay be captured by the imaging system. For example, eye-tracking unit130 may include a non-coherent or coherent light source (e.g., a laserdiode) emitting light in the visible spectrum or infrared spectrum, anda camera capturing the light reflected by the user's eye. As anotherexample, eye-tracking unit 130 may capture reflected radio waves emittedby a miniature radar unit. Eye-tracking unit 130 may use low-power lightemitters that emit light at frequencies and intensities that would notinjure the eye or cause physical discomfort. Eye-tracking unit 130 maybe arranged to increase contrast in images of an eye captured byeye-tracking unit 130 while reducing the overall power consumed byeye-tracking unit 130 (e.g., reducing power consumed by a light emitterand an imaging system included in eye-tracking unit 130). For example,in some implementations, eye-tracking unit 130 may consume less than 100milliwatts of power.

Near-eye display 120 may use the orientation of the eye to, e.g.,determine an inter-pupillary distance (IPD) of the user, determine gazedirection, introduce depth cues (e.g., blur image outside of the user'smain line of sight), collect heuristics on the user interaction in theVR media (e.g., time spent on any particular subject, object, or frameas a function of exposed stimuli), some other functions that are basedin part on the orientation of at least one of the user's eyes, or anycombination thereof. Because the orientation may be determined for botheyes of the user, eye-tracking unit 130 may be able to determine wherethe user is looking. For example, determining a direction of a user'sgaze may include determining a point of convergence based on thedetermined orientations of the user's left and right eyes. A point ofconvergence may be the point where the two foveal axes of the user'seyes intersect. The direction of the user's gaze may be the direction ofa line passing through the point of convergence and the mid-pointbetween the pupils of the user's eyes.

Input/output interface 140 may be a device that allows a user to sendaction requests to console 110. An action request may be a request toperform a particular action. For example, an action request may be tostart or to end an application or to perform a particular action withinthe application. Input/output interface 140 may include one or moreinput devices. Example input devices may include a keyboard, a mouse, agame controller, a glove, a button, a touch screen, or any othersuitable device for receiving action requests and communicating thereceived action requests to console 110. An action request received bythe input/output interface 140 may be communicated to console 110, whichmay perform an action corresponding to the requested action. In someembodiments, input/output interface 140 may provide haptic feedback tothe user in accordance with instructions received from console 110. Forexample, input/output interface 140 may provide haptic feedback when anaction request is received, or when console 110 has performed arequested action and communicates instructions to input/output interface140. In some embodiments, external imaging device 150 may be used totrack input/output interface 140, such as tracking the location orposition of a controller (which may include, for example, an IR lightsource) or a hand of the user to determine the motion of the user. Insome embodiments, near-eye display 120 may include one or more imagingdevices to track input/output interface 140, such as tracking thelocation or position of a controller or a hand of the user to determinethe motion of the user.

Console 110 may provide content to near-eye display 120 for presentationto the user in accordance with information received from one or more ofexternal imaging device 150, near-eye display 120, and input/outputinterface 140. In the example shown in FIG. 1, console 110 may includean application store 112, a headset tracking module 114, an artificialreality engine 116, and an eye-tracking module 118. Some embodiments ofconsole 110 may include different or additional modules than thosedescribed in conjunction with FIG. 1. Functions further described belowmay be distributed among components of console 110 in a different mannerthan is described here.

In some embodiments, console 110 may include a processor and anon-transitory computer-readable storage medium storing instructionsexecutable by the processor. The processor may include multipleprocessing units executing instructions in parallel. The non-transitorycomputer-readable storage medium may be any memory, such as a hard diskdrive, a removable memory, or a solid-state drive (e.g., flash memory ordynamic random access memory (DRAM)). In various embodiments, themodules of console 110 described in conjunction with FIG. 1 may beencoded as instructions in the non-transitory computer-readable storagemedium that, when executed by the processor, cause the processor toperform the functions further described below.

Application store 112 may store one or more applications for executionby console 110. An application may include a group of instructions that,when executed by a processor, generates content for presentation to theuser. Content generated by an application may be in response to inputsreceived from the user via movement of the user's eyes or inputsreceived from the input/output interface 140. Examples of theapplications may include gaming applications, conferencing applications,video playback application, or other suitable applications.

Headset tracking module 114 may track movements of near-eye display 120using slow calibration information from external imaging device 150. Forexample, headset tracking module 114 may determine positions of areference point of near-eye display 120 using observed locators from theslow calibration information and a model of near-eye display 120.Headset tracking module 114 may also determine positions of a referencepoint of near-eye display 120 using position information from the fastcalibration information. Additionally, in some embodiments, headsettracking module 114 may use portions of the fast calibrationinformation, the slow calibration information, or any combinationthereof, to predict a future location of near-eye display 120. Headsettracking module 114 may provide the estimated or predicted futureposition of near-eye display 120 to artificial reality engine 116.

Artificial reality engine 116 may execute applications within artificialreality system environment 100 and receive position information ofnear-eye display 120, acceleration information of near-eye display 120,velocity information of near-eye display 120, predicted future positionsof near-eye display 120, or any combination thereof from headsettracking module 114. Artificial reality engine 116 may also receiveestimated eye position and orientation information from eye-trackingmodule 118. Based on the received information, artificial reality engine116 may determine content to provide to near-eye display 120 forpresentation to the user. For example, if the received informationindicates that the user has looked to the left, artificial realityengine 116 may generate content for near-eye display 120 that mirrorsthe user's eye movement in a virtual environment. Additionally,artificial reality engine 116 may perform an action within anapplication executing on console 110 in response to an action requestreceived from input/output interface 140, and provide feedback to theuser indicating that the action has been performed. The feedback may bevisual or audible feedback via near-eye display 120 or haptic feedbackvia input/output interface 140.

Eye-tracking module 118 may receive eye-tracking data from eye-trackingunit 130 and determine the position of the user's eye based on the eyetracking data. The position of the eye may include an eye's orientation,location, or both relative to near-eye display 120 or any elementthereof. Because the eye's axes of rotation change as a function of theeye's location in its socket, determining the eye's location in itssocket may allow eye-tracking module 118 to more accurately determinethe eye's orientation.

In some embodiments, eye-tracking module 118 may store a mapping betweenimages captured by eye-tracking system 130 and eye positions todetermine a reference eye position from an image captured byeye-tracking system 130. Alternatively or additionally, eye-trackingmodule 118 may determine an updated eye position relative to a referenceeye position by comparing an image from which the reference eye positionis determined to an image from which the updated eye position is to bedetermined. Eye-tracking module 118 may determine eye position usingmeasurements from different imaging devices or other sensors. Forexample, eye-tracking module 118 may use measurements from a sloweye-tracking system to determine a reference eye position, and thendetermine updated positions relative to the reference eye position froma fast eye-tracking system until a next reference eye position isdetermined based on measurements from the slow eye-tracking system.

Eye-tracking module 118 may also determine eye calibration parameters toimprove precision and accuracy of eye tracking. Eye calibrationparameters may include parameters that may change whenever a user donsor adjusts near-eye display system 120. Example eye calibrationparameters may include an estimated distance between a component ofeye-tracking system 130 and one or more parts of the eye, such as theeye's center, pupil, cornea boundary, or a point on the surface of theeye. Other example eye calibration parameters may be specific to a userand may include an estimated average eye radius, an average cornealradius, an average sclera radius, a map of features on the eye surface,and an estimated eye surface contour. In embodiments where light fromthe outside of near-eye display system 120 may reach the eye (as in someaugmented reality applications), the calibration parameters may includecorrection factors for intensity and color balance due to variations inlight from the outside of near-eye display system 120. Eye-trackingmodule 118 may use eye calibration parameters to determine whether themeasurements captured by eye-tracking system 130 would alloweye-tracking module 118 to determine an accurate eye position (alsoreferred to herein as “valid measurements”). Invalid measurements, fromwhich eye-tracking module 118 may not be able to determine an accurateeye position, may be caused by the user blinking, adjusting the headset,or removing the headset, and/or may be caused by near-eye display system120 experiencing greater than a threshold change in illumination due toexternal light. In some embodiments, at least some of the functions ofeye-tracking module 118 may be performed by eye-tracking system 130.

FIG. 2 is a perspective view of an example of a near-eye display in theform of an HMD device 200 for implementing some of the examplesdisclosed herein. HMD device 200 may be a part of, e.g., a VR system, anAR system, an MR system, or any combination thereof. HMD device 200 mayinclude a body 220 and a head strap 230. FIG. 2 shows a bottom side 223,a front side 225, and a left side 227 of body 220 in the perspectiveview. Head strap 230 may have an adjustable or extendible length. Theremay be a sufficient space between body 220 and head strap 230 of HMDdevice 200 for allowing a user to mount HMD device 200 onto the user'shead. In various embodiments, HMD device 200 may include additional,fewer, or different components. For example, in some embodiments, HMDdevice 200 may include eyeglass temples and temple tips as shown in, forexample, FIG. 3 below, rather than head strap 230.

HMD device 200 may present to a user media including virtual and/oraugmented views of a physical, real-world environment withcomputer-generated elements. Examples of the media presented by HMDdevice 200 may include images (e.g., two-dimensional (2D) orthree-dimensional (3D) images), videos (e.g., 2D or 3D videos), audio,or any combination thereof. The images and videos may be presented toeach eye of the user by one or more display assemblies (not shown inFIG. 2) enclosed in body 220 of HMD device 200. In various embodiments,the one or more display assemblies may include a single electronicdisplay panel or multiple electronic display panels (e.g., one displaypanel for each eye of the user). Examples of the electronic displaypanel(s) may include, for example, an LCD, an OLED display, an ILEDdisplay, a μLED display, an AMOLED, a TOLED, some other display, or anycombination thereof. HMD device 200 may include two eye box regions.

In some implementations, HMD device 200 may include various sensors (notshown), such as depth sensors, motion sensors, position sensors, and eyetracking sensors. Some of these sensors may use a structured lightpattern for sensing. In some implementations, HMD device 200 may includean input/output interface for communicating with a console. In someimplementations, HMD device 200 may include a virtual reality engine(not shown) that can execute applications within HMD device 200 andreceive depth information, position information, accelerationinformation, velocity information, predicted future positions, or anycombination thereof of HMD device 200 from the various sensors. In someimplementations, the information received by the virtual reality enginemay be used for producing a signal (e.g., display instructions) to theone or more display assemblies. In some implementations, HMD device 200may include locators (not shown, such as locators 126) located in fixedpositions on body 220 relative to one another and relative to areference point. Each of the locators may emit light that is detectableby an external imaging device.

FIG. 3 is a perspective view of an example of a near-eye display 300 inthe form of a pair of glasses for implementing some of the examplesdisclosed herein. Near-eye display 300 may be a specific implementationof near-eye display 120 of FIG. 1, and may be configured to operate as avirtual reality display, an augmented reality display, and/or a mixedreality display. Near-eye display 300 may include a frame 305 and adisplay 310. Display 310 may be configured to present content to a user.In some embodiments, display 310 may include display electronics and/ordisplay optics. For example, as described above with respect to near-eyedisplay 120 of FIG. 1, display 310 may include an LCD display panel, anLED display panel, or an optical display panel (e.g., a waveguidedisplay assembly).

Near-eye display 300 may further include various sensors 350 a, 350 b,350 c, 350 d, and 350 e on or within frame 305. In some embodiments,sensors 350 a-350 e may include one or more depth sensors, motionsensors, position sensors, inertial sensors, or ambient light sensors.In some embodiments, sensors 350 a-350 e may include one or more imagesensors configured to generate image data representing different fieldsof views in different directions. In some embodiments, sensors 350 a-350e may be used as input devices to control or influence the displayedcontent of near-eye display 300, and/or to provide an interactiveVR/AR/MR experience to a user of near-eye display 300. In someembodiments, sensors 350 a-350 e may also be used for stereoscopicimaging.

In some embodiments, near-eye display 300 may further include one ormore illuminators 330 to project light into the physical environment.The projected light may be associated with different frequency bands(e.g., visible light, infra-red light, ultra-violet light, etc.), andmay serve various purposes. For example, illuminator(s) 330 may projectlight in a dark environment (or in an environment with low intensity ofinfra-red light, ultra-violet light, etc.) to assist sensors 350 a-350 ein capturing images of different objects within the dark environment. Insome embodiments, illuminator(s) 330 may be used to project certainlight patterns onto the objects within the environment. In someembodiments, illuminator(s) 330 may be used as locators, such aslocators 126 described above with respect to FIG. 1.

In some embodiments, near-eye display 300 may also include ahigh-resolution camera 340. Camera 340 may capture images of thephysical environment in the field of view. The captured images may beprocessed, for example, by a virtual reality engine (e.g., artificialreality engine 116 of FIG. 1) to add virtual objects to the capturedimages or modify physical objects in the captured images, and theprocessed images may be displayed to the user by display 310 for AR orMR applications.

FIG. 4 illustrates an example of an optical see-through augmentedreality system 400 including a waveguide display according to certainembodiments. Augmented reality system 400 may include a projector 410and a combiner 415. Projector 410 may include a light source or imagesource 412 and projector optics 414. In some embodiments, light sourceor image source 412 may include one or more micro-LED devices describedabove. In some embodiments, image source 412 may include a plurality ofpixels that displays virtual objects, such as an LCD display panel or anLED display panel. In some embodiments, image source 412 may include alight source that generates coherent or partially coherent light. Forexample, image source 412 may include a laser diode, a vertical cavitysurface emitting laser, an LED, and/or a micro-LED described above. Insome embodiments, image source 412 may include a plurality of lightsources (e.g., an array of micro-LEDs described above), each emitting amonochromatic image light corresponding to a primary color (e.g., red,green, or blue). In some embodiments, image source 412 may include threetwo-dimensional arrays of micro-LEDs, where each two-dimensional arrayof micro-LEDs may include micro-LEDs configured to emit light of aprimary color (e.g., red, green, or blue). In some embodiments, imagesource 412 may include an optical pattern generator, such as a spatiallight modulator. Projector optics 414 may include one or more opticalcomponents that can condition the light from image source 412, such asexpanding, collimating, scanning, or projecting light from image source412 to combiner 415. The one or more optical components may include, forexample, one or more lenses, liquid lenses, mirrors, apertures, and/orgratings. For example, in some embodiments, image source 412 may includeone or more one-dimensional arrays or elongated two-dimensional arraysof micro-LEDs, and projector optics 414 may include one or moreone-dimensional scanners (e.g., micro-mirrors or prisms) configured toscan the one-dimensional arrays or elongated two-dimensional arrays ofmicro-LEDs to generate image frames. In some embodiments, projectoroptics 414 may include a liquid lens (e.g., a liquid crystal lens) witha plurality of electrodes that allows scanning of the light from imagesource 412.

Combiner 415 may include an input coupler 430 for coupling light fromprojector 410 into a substrate 420 of combiner 415. Combiner 415 maytransmit at least 50% of light in a first wavelength range and reflectat least 25% of light in a second wavelength range. For example, thefirst wavelength range may be visible light from about 400 nm to about650 nm, and the second wavelength range may be in the infrared band, forexample, from about 800 nm to about 1000 nm. Input coupler 430 mayinclude a volume holographic grating, a diffractive optical element(DOE) (e.g., a surface-relief grating), a slanted surface of substrate420, or a refractive coupler (e.g., a wedge or a prism). For example,input coupler 430 may include a reflective volume Bragg grating or atransmissive volume Bragg grating. Input coupler 430 may have a couplingefficiency of greater than 30%, 50%, 75%, 90%, or higher for visiblelight. Light coupled into substrate 420 may propagate within substrate420 through, for example, total internal reflection (TIR). Substrate 420may be in the form of a lens of a pair of eyeglasses. Substrate 420 mayhave a flat or a curved surface, and may include one or more types ofdielectric materials, such as glass, quartz, plastic, polymer,poly(methyl methacrylate) (PMMA), crystal, or ceramic. A thickness ofthe substrate may range from, for example, less than about 1 mm to about10 mm or more. Substrate 420 may be transparent to visible light.

Substrate 420 may include or may be coupled to a plurality of outputcouplers 440, each configured to extract at least a portion of the lightguided by and propagating within substrate 420 from substrate 420, anddirect extracted light 460 to an eyebox 495 where an eye 490 of the userof augmented reality system 400 may be located when augmented realitysystem 400 is in use. The plurality of output couplers 440 may replicatethe exit pupil to increase the size of eyebox 495 such that thedisplayed image is visible in a larger area. As input coupler 430,output couplers 440 may include grating couplers (e.g., volumeholographic gratings or surface-relief gratings), other diffractionoptical elements (DOEs), prisms, etc. For example, output couplers 440may include reflective volume Bragg gratings or transmissive volumeBragg gratings. Output couplers 440 may have different coupling (e.g.,diffraction) efficiencies at different locations. Substrate 420 may alsoallow light 450 from the environment in front of combiner 415 to passthrough with little or no loss. Output couplers 440 may also allow light450 to pass through with little loss. For example, in someimplementations, output couplers 440 may have a very low diffractionefficiency for light 450 such that light 450 may be refracted orotherwise pass through output couplers 440 with little loss, and thusmay have a higher intensity than extracted light 460. In someimplementations, output couplers 440 may have a high diffractionefficiency for light 450 and may diffract light 450 in certain desireddirections (i.e., diffraction angles) with little loss. As a result, theuser may be able to view combined images of the environment in front ofcombiner 415 and images of virtual objects projected by projector 410.

FIG. 5A illustrates an example of a near-eye display (NED) device 500including a waveguide display 530 according to certain embodiments. NEDdevice 500 may be an example of near-eye display 120, augmented realitysystem 400, or another type of display device. NED device 500 mayinclude a light source 510, projection optics 520, and waveguide display530. Light source 510 may include multiple panels of light emitters fordifferent colors, such as a panel of red light emitters 512, a panel ofgreen light emitters 514, and a panel of blue light emitters 516. Thered light emitters 512 are organized into an array; the green lightemitters 514 are organized into an array; and the blue light emitters516 are organized into an array. The dimensions and pitches of lightemitters in light source 510 may be small. For example, each lightemitter may have a diameter less than 2 μm (e.g., about 1.2 μm) and thepitch may be less than 2 μm (e.g., about 1.5 μm). As such, the number oflight emitters in each red light emitters 512, green light emitters 514,and blue light emitters 516 can be equal to or greater than the numberof pixels in a display image, such as 960×720, 1280×720, 1440×1080,1920×1080, 2160×1080, or 2560×1080 pixels. Thus, a display image may begenerated simultaneously by light source 510. A scanning element may notbe used in NED device 500.

Before reaching waveguide display 530, the light emitted by light source510 may be conditioned by projection optics 520, which may include alens array. Projection optics 520 may collimate or focus the lightemitted by light source 510 to waveguide display 530, which may includea coupler 532 for coupling the light emitted by light source 510 intowaveguide display 530. The light coupled into waveguide display 530 maypropagate within waveguide display 530 through, for example, totalinternal reflection as described above with respect to FIG. 4. Coupler532 may also couple portions of the light propagating within waveguidedisplay 530 out of waveguide display 530 and towards user's eye 590.

FIG. 5B illustrates an example of a near-eye display (NED) device 550including a waveguide display 580 according to certain embodiments. Insome embodiments, NED device 550 may use a scanning mirror 570 toproject light from a light source 540 to an image field where a user'seye 590 may be located. NED device 550 may be an example of near-eyedisplay 120, augmented reality system 400, or another type of displaydevice. Light source 540 may include one or more rows or one or morecolumns of light emitters of different colors, such as multiple rows ofred light emitters 542, multiple rows of green light emitters 544, andmultiple rows of blue light emitters 546. For example, red lightemitters 542, green light emitters 544, and blue light emitters 546 mayeach include N rows, each row including, for example, 2560 lightemitters (pixels). The red light emitters 542 are organized into anarray; the green light emitters 544 are organized into an array; and theblue light emitters 546 are organized into an array. In someembodiments, light source 540 may include a single line of lightemitters for each color. In some embodiments, light source 540 mayinclude multiple columns of light emitters for each of red, green, andblue colors, where each column may include, for example, 1080 lightemitters. In some embodiments, the dimensions and/or pitches of thelight emitters in light source 540 may be relatively large (e.g., about3-5 μm) and thus light source 540 may not include sufficient lightemitters for simultaneously generating a full display image. Forexample, the number of light emitters for a single color may be fewerthan the number of pixels (e.g., 2560×1080 pixels) in a display image.The light emitted by light source 540 may be a set of collimated ordiverging beams of light.

Before reaching scanning mirror 570, the light emitted by light source540 may be conditioned by various optical devices, such as collimatinglenses or a freeform optical element 560. Freeform optical element 560may include, for example, a multi-facet prism or another light foldingelement that may direct the light emitted by light source 540 towardsscanning mirror 570, such as changing the propagation direction of thelight emitted by light source 540 by, for example, about 90° or larger.In some embodiments, freeform optical element 560 may be rotatable toscan the light. Scanning mirror 570 and/or freeform optical element 560may reflect and project the light emitted by light source 540 towaveguide display 580, which may include a coupler 582 for coupling thelight emitted by light source 540 into waveguide display 580. The lightcoupled into waveguide display 580 may propagate within waveguidedisplay 580 through, for example, total internal reflection as describedabove with respect to FIG. 4. Coupler 582 may also couple portions ofthe light propagating within waveguide display 580 out of waveguidedisplay 580 and towards user's eye 590.

Scanning mirror 570 may include a microelectromechanical system (MEMS)mirror or any other suitable mirrors. Scanning mirror 570 may rotate toscan in one or two dimensions. As scanning mirror 570 rotates, the lightemitted by light source 540 may be directed to a different area ofwaveguide display 580 such that a full display image may be projectedonto waveguide display 580 and directed to user's eye 590 by waveguidedisplay 580 in each scanning cycle. For example, in embodiments wherelight source 540 includes light emitters for all pixels in one or morerows or columns, scanning mirror 570 may be rotated in the column or rowdirection (e.g., x or y direction) to scan an image. In embodimentswhere light source 540 includes light emitters for some but not allpixels in one or more rows or columns, scanning mirror 570 may berotated in both the row and column directions (e.g., both x and ydirections) to project a display image (e.g., using a raster-typescanning pattern).

NED device 550 may operate in predefined display periods. A displayperiod (e.g., display cycle) may refer to a duration of time in which afull image is scanned or projected. For example, a display period may bea reciprocal of the desired frame rate. In NED device 550 that includesscanning mirror 570, the display period may also be referred to as ascanning period or scanning cycle. The light generation by light source540 may be synchronized with the rotation of scanning mirror 570. Forexample, each scanning cycle may include multiple scanning steps, wherelight source 540 may generate a different light pattern in eachrespective scanning step.

In each scanning cycle, as scanning mirror 570 rotates, a display imagemay be projected onto waveguide display 580 and user's eye 590. Theactual color value and light intensity (e.g., brightness) of a givenpixel location of the display image may be an average of the light beamsof the three colors (e.g., red, green, and blue) illuminating the pixellocation during the scanning period. After completing a scanning period,scanning mirror 570 may revert back to the initial position to projectlight for the first few rows of the next display image or may rotate ina reverse direction or scan pattern to project light for the nextdisplay image, where a new set of driving signals may be fed to lightsource 540. The same process may be repeated as scanning mirror 570rotates in each scanning cycle. As such, different images may beprojected to user's eye 590 in different scanning cycles.

FIG. 6 illustrates an example of an image source assembly 610 in anear-eye display system 600 according to certain embodiments. Imagesource assembly 610 may include, for example, a display panel 640 thatmay generate display images to be projected to the user's eyes, and aprojector 650 that may project the display images generated by displaypanel 640 to a waveguide display as described above with respect toFIGS. 4-5B. Display panel 640 may include a light source 642 and adriver circuit 644 for light source 642. Light source 642 may include,for example, light source 510 or 540. Projector 650 may include, forexample, freeform optical element 560, scanning mirror 570, and/orprojection optics 520 described above. Near-eye display system 600 mayalso include a controller 620 that synchronously controls light source642 and projector 650 (e.g., scanning mirror 570). Image source assembly610 may generate and output an image light to a waveguide display (notshown in FIG. 6), such as waveguide display 530 or 580. As describedabove, the waveguide display may receive the image light at one or moreinput-coupling elements, and guide the received image light to one ormore output-coupling elements. The input and output coupling elementsmay include, for example, a diffraction grating, a holographic grating,a prism, or any combination thereof. The input-coupling element may bechosen such that total internal reflection occurs with the waveguidedisplay. The output-coupling element may couple portions of the totalinternally reflected image light out of the waveguide display.

As described above, light source 642 may include a plurality of lightemitters arranged in an array or a matrix. Each light emitter may emitmonochromatic light, such as red light, blue light, green light,infra-red light, and the like. While RGB colors are often discussed inthis disclosure, embodiments described herein are not limited to usingred, green, and blue as primary colors. Other colors can also be used asthe primary colors of near-eye display system 600. In some embodiments,a display panel in accordance with an embodiment may use more than threeprimary colors. Each pixel in light source 642 may include threesubpixels that include a red micro-LED, a green micro-LED, and a bluemicro-LED. A semiconductor LED generally includes an active lightemitting layer within multiple layers of semiconductor materials. Themultiple layers of semiconductor materials may include differentcompound materials or a same base material with different dopants and/ordifferent doping densities. For example, the multiple layers ofsemiconductor materials may include an n-type material layer, an activeregion that may include hetero-structures (e.g., one or more quantumwells), and a p-type material layer. The multiple layers ofsemiconductor materials may be grown on a surface of a substrate havinga certain orientation. In some embodiments, to increase light extractionefficiency, a mesa that includes at least some of the layers ofsemiconductor materials may be formed.

Controller 620 may control the image rendering operations of imagesource assembly 610, such as the operations of light source 642 and/orprojector 650. For example, controller 620 may determine instructionsfor image source assembly 610 to render one or more display images. Theinstructions may include display instructions and scanning instructions.In some embodiments, the display instructions may include an image file(e.g., a bitmap file). The display instructions may be received from,for example, a console, such as console 110 described above with respectto FIG. 1. The scanning instructions may be used by image sourceassembly 610 to generate image light. The scanning instructions mayspecify, for example, a type of a source of image light (e.g.,monochromatic or polychromatic), a scanning rate, an orientation of ascanning apparatus, one or more illumination parameters, or anycombination thereof. Controller 620 may include a combination ofhardware, software, and/or firmware not shown here so as not to obscureother aspects of the present disclosure.

In some embodiments, controller 620 may be a graphics processing unit(GPU) of a display device. In other embodiments, controller 620 may beother kinds of processors. The operations performed by controller 620may include taking content for display and dividing the content intodiscrete sections. Controller 620 may provide to light source 642scanning instructions that include an address corresponding to anindividual source element of light source 642 and/or an electrical biasapplied to the individual source element. Controller 620 may instructlight source 642 to sequentially present the discrete sections usinglight emitters corresponding to one or more rows of pixels in an imageultimately displayed to the user. Controller 620 may also instructprojector 650 to perform different adjustments of the light. Forexample, controller 620 may control projector 650 to scan the discretesections to different areas of a coupling element of the waveguidedisplay (e.g., waveguide display 580) as described above with respect toFIG. 5B. As such, at the exit pupil of the waveguide display, eachdiscrete portion is presented in a different respective location. Whileeach discrete section is presented at a different respective time, thepresentation and scanning of the discrete sections occur fast enoughsuch that a user's eye may integrate the different sections into asingle image or series of images.

Image processor 630 may be a general-purpose processor and/or one ormore application-specific circuits that are dedicated to performing thefeatures described herein. In one embodiment, a general-purposeprocessor may be coupled to a memory to execute software instructionsthat cause the processor to perform certain processes described herein.In another embodiment, image processor 630 may be one or more circuitsthat are dedicated to performing certain features. While image processor630 in FIG. 6 is shown as a stand-alone unit that is separate fromcontroller 620 and driver circuit 644, image processor 630 may be asub-unit of controller 620 or driver circuit 644 in other embodiments.In other words, in those embodiments, controller 620 or driver circuit644 may perform various image processing functions of image processor630. Image processor 630 may also be referred to as an image processingcircuit.

In the example shown in FIG. 6, light source 642 may be driven by drivercircuit 644, based on data or instructions (e.g., display and scanninginstructions) sent from controller 620 or image processor 630. In oneembodiment, driver circuit 644 may include a circuit panel that connectsto and mechanically holds various light emitters of light source 642.Light source 642 may emit light in accordance with one or moreillumination parameters that are set by the controller 620 andpotentially adjusted by image processor 630 and driver circuit 644. Anillumination parameter may be used by light source 642 to generatelight. An illumination parameter may include, for example, sourcewavelength, pulse rate, pulse amplitude, beam type (continuous orpulsed), other parameter(s) that may affect the emitted light, or anycombination thereof. In some embodiments, the source light generated bylight source 642 may include multiple beams of red light, green light,and blue light, or any combination thereof.

Projector 650 may perform a set of optical functions, such as focusing,combining, conditioning, or scanning the image light generated by lightsource 642. In some embodiments, projector 650 may include a combiningassembly, a light conditioning assembly, or a scanning mirror assembly.Projector 650 may include one or more optical components that opticallyadjust and potentially re-direct the light from light source 642. Oneexample of the adjustment of light may include conditioning the light,such as expanding, collimating, correcting for one or more opticalerrors (e.g., field curvature, chromatic aberration, etc.), some otheradjustments of the light, or any combination thereof. The opticalcomponents of projector 650 may include, for example, lenses, mirrors,apertures, gratings, or any combination thereof.

Projector 650 may redirect image light via its one or more reflectiveand/or refractive portions so that the image light is projected atcertain orientations toward the waveguide display. The location wherethe image light is redirected toward the waveguide display may depend onspecific orientations of the one or more reflective and/or refractiveportions. In some embodiments, projector 650 includes a single scanningmirror that scans in at least two dimensions. In other embodiments,projector 650 may include a plurality of scanning mirrors that each scanin directions orthogonal to each other. Projector 650 may perform araster scan (horizontally or vertically), a bi-resonant scan, or anycombination thereof. In some embodiments, projector 650 may perform acontrolled vibration along the horizontal and/or vertical directionswith a specific frequency of oscillation to scan along two dimensionsand generate a two-dimensional projected image of the media presented touser's eyes. In other embodiments, projector 650 may include a lens orprism that may serve similar or the same function as one or morescanning mirrors. In some embodiments, image source assembly 610 may notinclude a projector, where the light emitted by light source 642 may bedirectly incident on the waveguide display.

In semiconductor LEDs, photons are usually generated at a certaininternal quantum efficiency through the recombination of electrons andholes within an active region (e.g., one or more semiconductor layers),where the internal quantum efficiency is the proportion of the radiativeelectron-hole recombination in the active region that emits photons. Thegenerated light may then be extracted from the LEDs in a particulardirection or within a particular solid angle. The ratio between thenumber of emitted photons extracted from an LED and the number ofelectrons passing through the LED is referred to as the external quantumefficiency, which describes how efficiently the LED converts injectedelectrons to photons that are extracted from the device.

The external quantum efficiency may be proportional to the injectionefficiency, the internal quantum efficiency, and the extractionefficiency. The injection efficiency refers to the proportion ofelectrons passing through the device that are injected into the activeregion. The extraction efficiency is the proportion of photons generatedin the active region that escape from the device. For LEDs, and inparticular, micro-LEDs with reduced physical dimensions, improving theinternal and external quantum efficiency and/or controlling the emissionspectrum may be challenging. In some embodiments, to increase the lightextraction efficiency, a mesa that includes at least some of the layersof semiconductor materials may be formed.

FIG. 7 is a cross-sectional view of an example of a near-eye displaysystem 700 according to certain embodiments. Near-eye display system 700may include at least one display assembly 710. Display assembly 710 maybe configured to direct image light (i.e., display light) to an eyeboxlocated at exit pupil 730 of near-eye display system 700 and to user'seye 720. It is noted that, even though FIG. 7 and other figures in thepresent disclosure show an eye of a user of a near-eye display systemfor illustration purposes, the eye of the user is not a part of thecorresponding near-eye display system.

As HMD device 200 and near-eye display system 300, near-eye displaysystem 700 may include a frame 705 and a display assembly 710 thatincludes a display 712 and/or display optics 714 coupled to or embeddedin frame 705. As described above, display 712 may display images to theuser electrically (e.g., using LCD) or optically (e.g., using awaveguide display and optical couplers as described with respect to FIG.4) according to data received from a console, such as console 110.Display 712 may include sub-pixels to emit light of a predominant color,such as red, green, blue, white, or yellow. In some embodiments, displayassembly 710 may include a stack of one or more waveguide displaysincluding, but not restricted to, a stacked waveguide display, avarifocal waveguide display, etc. The stacked waveguide display mayinclude a polychromatic display (e.g., a red-green-blue (RGB) display)created by stacking waveguide displays whose respective monochromaticsources are of different colors. The stacked waveguide display may alsobe a polychromatic display that can be projected on multiple planes(e.g. multi-planar colored display). In some configurations, the stackedwaveguide display may be a monochromatic display that can be projectedon multiple planes (e.g. multi-planar monochromatic display). Thevarifocal waveguide display is a display that can adjust a focalposition of image light emitted from the waveguide display. In alternateembodiments, display assembly 710 may include the stacked waveguidedisplay and the varifocal waveguide display.

Display optics 714 may be similar to display optics 124 and may displayimage content optically (e.g., using optical waveguides and opticalcouplers), or may correct optical errors associated with the imagelight, combine images of virtual objects and real objects, and presentthe corrected image light to exit pupil 730 of near-eye display system700, where the user's eye 720 may be located at. Display optics 714 mayalso relay the image generated by display 712 to create virtual imagesthat appear to be away from the image source and further than just a fewcentimeters away from the eyes of the user. For example, display optics714 may collimate light from the image source or project the displayedimage to create a virtual image that may appear to be far away andconvert spatial information of the displayed virtual objects intoangular information. Display optics 714 may also magnify the imagesource to make the image appear larger than the actual size of the imagesource.

There may be several types of eye measurements for determining userintent, cognitive processes, behavior, attention, etc. Thesemeasurements may include, for example, measurement related to fixations,where the eyes are stationary between movements and visual input mayoccur. Fixation-related measurement variables may include, for example,total fixation duration, mean fixation duration, fixation spatialdensity, number of areas fixated, fixation sequences, and fixation rate.The eye measurements may also include measurements of saccades, whichare rapid eye movements that occur between fixations. Saccade relatedparameters may include, for example, saccade number, amplitude,velocity, acceleration, and fixation-saccade ratio. The eye measurementsmay also include measurements of scanpath, which may include a series ofshort fixations and saccades alternating before the eyes reach a targetlocation on the display screen. Movement measures derived from scanpathmay include, for example, scanpath direction, duration, length, and areacovered. The eye movement measurements may further include measuring thesum of all fixations made in an area of interest before the eyes leavethat area or the proportion of time spent in each area. The eyemeasurements may also include measuring pupil size and blink rate, whichmay be used to study cognitive workload.

In addition, as described above, in an artificial reality system, toimprove user interaction with presented content, the artificial realitysystem may track the user's eye and modify or generate content based ona location or a direction in which the user is looking. Tracking the eyemay include tracking the position and/or shape of the pupil and/or thecornea of the eye, and determining the rotational position or gazedirection of the eye. One technique (referred to as Pupil Center CornealReflection or PCCR method) involves using MR LEDs to produce glints onthe eye cornea surface and then capturing images/videos of the eyeregion. Gaze direction can be estimated from the relative movementbetween the pupil center and glints.

FIG. 8 illustrates light reflections and scattering 800 by an eye 850during eye tracking using an eye-tracking system 810, which may beincluded in eye-tracking unit 130. Eye-tracking system 810 may include alight source 812 and a camera 814 as described above. In otherembodiments, eye-tracking system 810 may include different and/oradditional components than those depicted in FIG. 8. Light source 812may include, for example, a laser, an LED, or VCSELs, and may be mountedat a laser angle 822 relative to a surface normal vector 820 of eye 850.Surface normal vector 820 is orthogonal to a portion of the surface(e.g., cornea 852) of eye 850 illuminated by light source 812. In theexample shown in FIG. 8, surface normal vector 820 may be the same asthe pupillary axis (also referred to as optical axis, which may be aline passing through the center of pupil 856 and the center of cornea852) of eye 850. Laser angle 822 may be measured between surface normalvector 820 and a line from a center of the portion of the surface of eye850 illuminated by light source 812 to a center of the output apertureof light source 812. Camera 814 may be mounted at a camera angle 824relative to surface normal vector 820 of eye 850. Camera angle 824 maybe measured between surface normal vector 820 and a line from a centerof the portion of the surface of eye 850 illuminated by light source 812to a center of the image sensor or light input aperture of camera 814.In some embodiments, a difference between laser angle 822 and cameraangle 824 is less than a threshold amount so that camera 814 may captureimages via specular reflections of light incident on cornea 852 of eye850, which may beneficially increase contrast of the resulting image andminimize light power loss and power consumption.

The light emitted by light source 812 may substantially uniformlyilluminate a portion of the eye surface (e.g., cornea 852). A portion ofthe emitted light may be reflected specularly by cornea 852 of eye 850and captured by camera 814. In some cases, the light incident on eye 850may propagate into the eye for a small distance before being reflected.For example, at least some portions of the light may enter eye 850through cornea 852 and reach iris 854, pupil 856, lens 858, or retina860 of eye 850. Because some interfaces within eye 850 (e.g., surface ofiris 854) may be rough (e.g., due to features such as capillaries orbumps), the interfaces within eye 850 may scatter the incident light inmultiple directions. Different portions of the eye surface and theinterfaces within eye 850 may have different patterns of features. Thus,an intensity pattern of the light reflected by eye 850 may depend on thepattern of features within the illuminated portion of eye 850, which mayallow identification of the portions of the eye (e.g., iris 854 or pupil856) from the intensity pattern.

Camera 814 may collect and project light reflected by the illuminatedportion of eye 850 onto an image sensor of camera 814. Camera 814 mayalso correct one or more optical errors (such as those described withrespect to the display optics 124) to improve the contrast and otherproperties of the images captured by the image sensor of camera 814. Insome embodiments, camera 814 may also magnify the reflected light. Insome embodiments, camera 814 may enlarge the images. The image sensor ofcamera 814 may capture incident light focused by a lens assembly ofcamera 814. Thus, camera 814 may effectively capture an image of lightsource 812 (the emitted light of which is reflected specularly by thecornea of the eye) reflected by the eye, resulting in a “glint” in thecaptured image. Because of the scattering (diffusive reflections) atsome interfaces of the eye, light incident on a point of the imagesensor may include light reflected from multiple points within theilluminated portion of eye 850, and thus may be the result of theinterference of the light reflected from the multiple points. Thus, insome embodiments, the image sensor of camera 814 may also capture adiffraction or speckle pattern formed by a combination of lightreflected from multiple points of the surface of eye 850.

Each pixel of the image sensor may include a light-sensitive circuitthat can output a current or voltage signal corresponding to theintensity of the light incident on the pixel. In some embodiments, thepixels of the image sensor may be sensitive to light in a narrowwavelength band. In some other embodiments, the pixels of the imagesensor may have a wide-band or multi-band sensitivity. For example, theimage sensor of camera 814 may include a complementary metal-oxidesemiconductor (CMOS) pixel array, which may be used with light having awavelength less than about 850 nm. As another example, the image sensorof camera 814 may include an indium gallium arsenide (InGaAs) alloypixel array or a charge-coupled device (CCD). Such an image sensor maybe used with a laser emitting light having a wavelength between about900 nm and about 1160 nm.

In some embodiments, to determine a position change of eye 850, aneye-tracking module (e.g., eye-tracking unit 130 or eye-tracking module118 of FIG. 1) may determine a pixel shift between images. Multiplyingthe pixel shift by a calibrated distance per pixel may allow theeye-tracking module to determine a distance the surface (e.g., cornea852) of eye 850 has shifted. For example, if the glint captured in oneimage is shifted by two pixels relative to the glint captured in aprevious image, and each pixel corresponds to a distance of 10micrometers at the surface of eye 850, the surface of eye 850 may havemoved about 20 micrometers.

In some embodiments, eye-tracking techniques used in head-mounteddevices may be video-based and may be performed based on appearance orfeatures. For example, the appearance-based techniques may use certainmapping functions to map the entire eye image or a region of interest ofthe eye image to a gaze direction or point-of-gaze. The mapping functionmay have a high-dimensional input (e.g., the intensities of imagepixels) and a low-dimensional output (e.g., the gaze direction,point-of-gaze, etc.). These mapping functions may be based on machinelearning models, such as convolutional neural networks (CNNs).

The feature-based techniques may perform feature extraction and gazeestimation using the extracted features. The features can be any one ormore of the following: pupil center, iris center, pupil-iris boundary,iris-sclera boundary, first Purkinje images (reflections off the frontsurface of the cornea, known as corneal reflections or glints), fourthPurkinje images (reflections of the back surface of the crystallinelens), eye corners, and the like. These features may be extracted usingcomputer vision techniques (e.g., intensity histogram analysis,thresholding, edge detection, blob segmentation, convex-hull,morphological operations, shape fitting, deformable templates,centroiding, etc.) or machine-learning techniques, or any combination.The gaze estimation techniques can be interpolation-based ormodel-based. The interpolation-based techniques may use certain mappingfunctions (e.g., second degree bivariate polynomial) to map eye features(e.g., pupil center or pupil center-corneal reflection (PCCR) vector) tothe gaze direction. The coefficients of these mapping functions may beobtained through a personal calibration procedure that may involvecollecting data while the user fixates at a sequence of fixation targetswith known coordinates. This calibration may be performed for eachsubject and each session, and may sometimes be performed multiple timesin each session, because the calibration may be sensitive to slippage ofthe head-mounted device relative to the head. The mapping functions maythen use the calibration data points and interpolation techniques todetermine the gaze direction. The model-based methods may use models ofthe system (e.g., camera(s) and/or light source(s)) and the eye that mayinclude actual physical system parameters and anatomical eye parametersto determine a 3-D gaze from a set of eye features (e.g., pupil boundaryand multiple corneal reflections) according to 3-D geometry. Model-basedtechniques may perform both a one-time system calibration and a one-timepersonal calibration for each user. The data collection procedure forthe personal calibration may be similar to that of theinterpolation-based methods.

Alternatively or additionally, the eye-tracking module may determine theposition of the eye in a captured image by comparing the captured imageswith one or more previous images having known positions of the eye. Forexample, the eye-tracking module may include a database of images thatare each associated with a reference eye position. By matching thecaptured image with a stored image, the eye-tracking module maydetermine that the eye is at the reference eye position associated withthe stored image. In some embodiments, the eye-tracking module mayidentify a feature in a portion of a captured image. The feature mayinclude a diffraction or optical flow pattern associated with aparticular portion of eye 850, such as the pupil or the iris. Forexample, the eye-tracking module may determine the eye position byretrieving a reference eye position associated with the feature (whichwas also captured in a reference image), determining a pixel shiftbetween the feature in the captured image and the feature in thereference image, and determining the eye position based on thedetermined pixel shift with respect to the reference eye position andthe calibrated distance per pixel as described above.

As discussed above, camera 814 may effectively capture an image of lightsource 812 reflected by cornea 852 of eye 850. In some embodiments, theeye-tracking module may determine a gaze direction of the user's eyebased on the locations of the images of the light sources (e.g., glints)on cornea 852 in the captured image. The gaze direction may bedetermined by a foveal axis 826 of the user's eyes, where foveal axis826 (also referred to as “visual axis”) may be a line passing throughthe center of pupil 856 and the center of fovea 862.

FIG. 9 is a simplified flowchart 900 illustrating an example method fortracking the eye of a user of a near-eye display system according tocertain embodiments. The operations in flowchart 900 may be performedby, for example, eye-tracking unit 130 or eye-tracking system 810described above. At block 910, one or more light sources may illuminatethe user's eye. In various embodiments, the light sources may be in thefield of view of the user's eye or at a periphery of the field of viewof the user's eye. In some embodiments, a light source may be located atthe periphery of the field of view of the user's eye, and the light fromthe light source may be guided and directed to the user's eye fromlocations in the field of view of the user's eye.

At block 920, an imaging device (e.g., a camera) may collect lightreflected by the user's eye and generate one or more images of theuser's eye. As described above, the cornea of the user's eye mayspecularly reflect the illumination light, while some portions of theuser's eye (e.g., iris) may diffusively scatter the illumination light.The images of the user's eye may include portions (e.g., the iris regionand/or the pupil portion) where the contrast may be different due to thescattering of the illumination light. The images of the user's eye mayalso include glints caused by the specular reflection of theillumination light by the user's cornea.

FIG. 10A illustrates an example of an image 1000 of a user's eyecaptured by a camera according to certain embodiments. Image 1000includes an iris region 1010, a pupil region 1020, and multiple glints1030. Glints 1030 may be caused by illumination light specularlyreflected off the cornea of the user's eye.

Optionally, at block 930, the eye-tracking system may perform systemcalibration to improve the precision and accuracy of the eye tracking asdescribed above with respect to eye-tracking module 118. The systemcalibration may include, for example, calibrating the eye trackingoptical path (such as extrinsic (e.g., position or orientation) andintrinsic camera parameters), positions of the light sources, thedisplay optical path (e.g., position of the display, extrinsic andintrinsic parameters of the display optics, etc.)

At block 940, the location of the center of the pupil of the user's eyemay be determined based on the scattering of the illumination light by,for example, the iris of the user's eye. As described above, theboundaries of the pupil and/or the iris may be determined based on imagesegmentation of the pupil region in the captured image as shown in FIG.10A. Based on the boundaries of the pupil, the location of the center ofthe pupil may be determined.

At block 950, the position of the cornea of the user's eye may bedetermined based on the locations of the glints in the captured image ofthe user's eye as shown in FIG. 10A. As described above, the locationsof the glints may be determined using, for example, a Gaussiancentroiding technique. The accuracy and precision of the determinedlocations of the glints may depend on the locations of the light sources(or virtual or effective light sources). Based on the locations of twoor more glints, the position of the cornea may be determined using, forexample, nonlinear optimization and based on the assumption that thecornea (in particular, the corneal apex) is close to a sphere.

FIG. 10B illustrates an example of an identified iris region 1040, anexample of an identified pupil region 1050, and examples of glintregions 1060 identified in image 1000 of the user's eye according tocertain embodiments. As illustrated, edges of iris region 1040 and pupilregion 1050 are identified. The center of pupil region 1020 may then bedetermined based on the edges of pupil region 1050 and/or iris region1040. The locations of glints 1030 can also be determined based on thelocations of glint regions 1060 identified in image 1000. Based on thelocations of glint regions 1060, the position of the center of thecornea may be determined.

Optionally, at block 960, the eye-tracking system may perform usercalibration to determine certain eye calibration parameters forimproving the precision and accuracy of eye tracking as described abovewith respect to eye-tracking module 118 and FIG. 8. The user calibrationmay include, for example, determining the eye model parameters (e.g.,anatomical eye parameters) or the coefficients of some mapping functionsthat may not depend on a particular eye parameter. Other examples of theeye calibration parameters may include an estimated average eye radius,an average corneal radius, an average sclera radius, a map of featureson the eye surface, and an estimated eye surface contour. As describedabove, a kappa angle between the pupillary axis (optical axis) and thefoveal axis (visual axis) of the use's eye may be different fordifferent users, and thus may need to be calibrated during thecalibration. In some embodiments, the calibration may be performed bydisplaying a set of target points distributed over a display screenaccording to a certain pattern, and the user is asked to gaze at each ofthe target points for a certain amount of time. The camera may capturethe corresponding eye positions for the target points, which are thenmapped to the corresponding gaze coordinates or directions, and theeye-tracking system may then learn the mapping function or the modelparameters. In some embodiments, the calibrations at block 930 and 960may only be performed once when the near-eye display system is put on ormoved.

At block 970, the gaze direction of the user's eye may be determinedbased on, for example, the location of the center of the pupil and theposition of the center of the cornea. In some embodiments, the pupillaryaxis of the use's eye may be determined first and may then be used todetermine the foveal axis (or line of sight, gaze direction, or visualaxis) of the user's eye, for example, based on an angle between thepupillary axis and the foveal axis.

Based on the gaze direction (and thus the center of the field of view)of the user's eye and the sensitivity of human eyes at different regionsof the retina, the display system may determine the luminance levels forthe individual light sources in different display zones of the displaysystem that correspond to different zones on the retina of a user's eye.The individual light sources in the different display zones may then becontrolled to emit at the different luminance levels. As describedabove, human eyes are generally less sensitive to light from largeviewing angles with respect to the foveal axis. The sensitivity may peakat the foveal zone and quickly decrease outside of the foveal zone.Therefore, display zones of a display panel that may be imaged ontoregions of the retina farther away from the fovea may not be verynoticeable to a user's eye even if these display zones have highluminance levels or high light intensities. As such, light sources(e.g., micro-LEDs or AMOLEDs) in these display zones may be controlledto emit light at lower luminance levels to reduce the power consumptionof the display system, with no or minimum impact on the user experience.Light sources in a display zone that may be imaged onto a zone of theretina including the fovea may be controlled to emit at a higherluminance level (or brightness). By reducing the luminance levels of thelight sources in some display zones of the display panel that may haveless impact on user experience, the power consumption of the displaysystem can be reduced.

FIG. 11 is a simplified block diagram of an example of a controller 1100for a near-eye display system according to certain embodiments. Thecontroller 1100 may be incorporated within the artificial reality engine116 described above. The controller 1100 may include an applicationprocessor 1120 and a display driver integrated circuit (DDIC) 1150. Thecontroller 1100 may receive data from an embedded sensor 1110 having asensor interface 1115. The embedded sensor 1110 may be incorporatedwithin the eye-tracking unit 130 and/or the eye-tracking system 810described above. The embedded sensor 1110 may use the method illustratedby flowchart 900 to track the position and the gaze direction (and thecenter of the field of view) of an eye of a user of the near-eye displaysystem. The embedded sensor 1110 may also perform a user calibration todetermine the location of a foveal axis and other characteristics of theeye of the user as described above.

The sensor interface 1115 of the embedded sensor 1110 may transmiteye-tracking and/or user calibration data to a sensor interface 1125 ofthe application processor 1120. The sensor interface of the applicationprocessor 1120 may then send the data to an authentication engine 1130,which may analyze the data to determine whether the data is accurate. Ifthe authentication engine 1130 determines that the data is accurate, theauthentication engine 1130 may route the data through a compositionengine 1135 and a display interface 1140 via a graphics pipeline 1145.In some embodiments, the composition engine 1135 may use the data todetermine a map for driving the light sources in the display asdiscussed in more detail below. For example, the composition engine 1135may maintain a lookup table that specifies the luminance bands fordifferent zones (e.g., based on the distances and/or the relativepositions of the different zones from a maximum luminance location), andmay use the lookup table and the center of the field of view of theuser's eye to determine a map that indicates the luminance bands fordifferent display zones of the display panel of the display system. Insome embodiments, the DDIC 1150 may use the data to determine the mapfor driving the light sources in the display. The display interface 1140may send the data and/or the map to a display interface 1155 of the DDIC1150.

The display interface 1155 of the DDIC 1150 may send the data and/or themap to a timing controller (T-CON) 1160. The timing controller 1160 mayuse the data and/or the map to provide instructions to a display gatedriver 1165 and a display source driver 1170, which may drive the lightsources in the display to emit light at luminance levels according tothe map. For example, display source driver 1170 and/or display gatedriver 1165 may perform gamma correction (e.g., apply display gamma tocorrect or offset image gamma) and provide drive currents or voltages tothe light sources, based on the luminance bands for the display zonesand transfer functions between input display values (e.g., gray levelsor drive levels) and luminance levels for the different display zones asdiscussed in detail below.

FIGS. 12A-12D illustrate examples of methods for driving light sourceswithin a display according to certain embodiments. FIG. 12A is a diagramof an example of a luminance pattern 1200 for a display according tocertain embodiments. The display may include a two-dimensional array ofindividual light sources, such as micro-LEDs or AMOLEDs. The lightsources may be controlled by respective driver circuits to emit light atdesired luminance levels. As shown in FIG. 12A, the luminance pattern1200 may include multiple zones, such as a first zone A, a second zoneB, and a third zone C. Although three zones are shown in the example inFIG. 12A, any number of zones greater than one may be used. In theexample shown in FIG. 12A, the zones may be arranged such that there isa maximum luminance location X at the center of the display, with theluminance level decreasing toward the edges of the display. The zonesmay be defined based on their locations with respect to the maximumluminance location X. In some embodiments, the zones may be definedbased on their distances from the maximum luminance location X. Forexample, as shown in FIG. 12A, the first zone A may include lightsources that are within a first radius r₁ from the maximum luminancelocation X, the second zone B may include light sources that are in aring having an inner radius r₁ and an outer radius r₂, and the thirdzone C may include light sources that are at a distance greater than thesecond radius r₂ from the maximum luminance location X, where the firstradius r₁ and the second radius r₂ originate at the maximum luminancelocation X. In some embodiments, the zones may be characterized byvarious alternative shapes, such as ovals, squares, and/or rectangles.

The maximum luminance location X may be at the center of the field ofview of the user's eye, on the foveal axis of the user's eye, or withina field of view of the fovea of the user's eye, such that location X maybe imaged onto the fovea of the retina of the user's eye. In the exampleshown in FIG. 12A, the center of the field of view of the user's eye maybe at the center of the display, and thus the maximum luminance locationX may be at the center of the display. In some embodiments, thecharacteristics of the user's eye (e.g., the foveal axis, optical axis,and/or field of view) may be determined based on the characteristics ofaverage human eye. Alternatively, the characteristics of a user's eyemay be determined based on various measurements, such as the usercalibration methods described above.

FIG. 12B is a diagram of another example of a luminance pattern 1205 fora display according to certain embodiments. As shown in FIG. 12B, theluminance pattern 1205 may include multiple zones, such as a first zoneA′, a second zone B′, and a third zone C′. Although three zones areshown in FIG. 12B, any number of zones greater than one may be used. Inthe example shown in FIG. 12B, the zones may be arranged such that thereis a maximum luminance location X′ at the center of the field of view ofthe user's eye, with the luminance decreasing toward the edges of thedisplay. The center of the field of view of the user's eye may bedetermined using the eye-tracking methods to determine the positionand/or the gaze direction of the user's eye as described above withrespect to, for example, FIG. 9. In the example shown in FIG. 12B, thecenter of the field of view of the user has shifted to the left side ofthe display as compared with the example shown in FIG. 12A. Thus, themaximum luminance location X′ may shift to the left side of the displaycorrespondingly to coincide with the center of the field of view of theuser's eye. The different display zones may be determined based on thelocations of the light sources with respect to the maximum luminancelocation X′. In some examples, the different display zones may bedetermined based on the distance from the light sources to the maximumluminance location X′. For example, as shown in FIG. 12B, the first zoneA′ may include light sources that are within a first radius r₁ from themaximum luminance location X′, the second zone B′ may include lightsources that are in a ring having an inner radius r₁ and an outer radiusr₂, and the third zone C′ may include light sources that are at adistance greater than the second radius r₂ from the maximum luminancelocation X′, where the first radius r₁ and the second radius r₂originate at the maximum luminance location X′. In some embodiments, thedifferent display zones may be characterized by various alternativeshapes, such as ovals, squares, and/or rectangles.

The maximum luminance location X′ may be on the foveal axis of theuser's eye. In some embodiments, the maximum luminance location X′ maybe within a field of view of the fovea of the user's eye. Thecharacteristics (e.g., the field of view) of the user's eye may bedetermined by the eye-tracking methods and/or the user calibrationmethods described above. The maximum luminance location X′ may bedetermined, for example, when the user first puts on the near-eyedisplay. Alternatively or additionally, the maximum luminance locationX′ may be determined at various subsequent times, such as when thelocation and/or the gaze direction of the user's eye changes.

FIG. 12C is a graph 1210 illustrating a transfer function between theluminance level and the display value (e.g., tone, gray level, or drivelevel) for light sources in a display system. Graph 1210 may be anexample of a transfer function for light sources that emit red, green,blue, or white light. The horizontal axis of graph 1210 is the inputdisplay value, which may be, for example, a gray level or a drive level,such as an integer between 0 and 255 that indicates a drive voltage orcurrent level within a drive voltage or current range. The transferfunction may not be a linear function and may be characterized by agamma value.

In the illustrated example, the transfer function may be the same forlight sources in the first zone A, the second zone B, and the third zoneC. Thus, a display value for any light source within the display mayresult in the driving of the light sources to emit at approximately thesame luminance level. For example, a display value GL for any lightsource within the display may result in driving the light source to emitat approximately a same luminance L₀, regardless of the location of thelight source within the display. In other words, the luminance level ofany light source receiving the same display value may be approximatelythe same. More specifically, the transfer function of the luminance as afunction of the display value is the same for light sources in the firstzone A, the second zone B, and the third zone C. Therefore, selectingthe drive value GL for any light source within the display may result indriving the light source to emit light at a same luminance L₀,regardless of whether the light source is within the first zone A, thesecond zone B, or the third zone C.

FIG. 12D is a graph 1215 illustrating the transfer functions between theluminance level and the display value (e.g., tone, gray level, or drivelevel) for light sources in a display according to certain embodiments.In the example shown in FIG. 12D, different transfer functions may beused for light sources in different zones. For example, a transferfunction for light sources in the first zone A (or A′) may be shown by acurve 1212, a transfer function for light sources in the second zone B(or B′) may be shown by a curve 1214, and a transfer function for lightsources in the third zone C (or C′) may be shown by a curve 1216. Curves1212, 1214, and 1216 may correspond to different luminance bands anddifferent gamma values.

Because of the different luminance bands and different transferfunctions for light sources in different zones, a same display value forlight sources within different zones may result in the driving of thelight sources within different zones at different voltage and/or currentlevels to emit light at different luminance levels. For example, settinga display value GL for a light source within zone A or A′ may result indriving the light source to emit light at a first luminance level L_(A),setting the display value GL for a light source within zone B or B′ mayresult in driving the light source to emit light at a second luminancelevel L_(B), and setting the display value GL for a light source withinzone C or C′ may result in driving the light source to emit light at athird luminance level L_(C). In this example, the first luminance L_(A)is greater than the second luminance L_(B), which in turn is greaterthan the third luminance L_(C).

When each of the first zone A, the second zone B, and the third zone Chas a respective discrete transfer function for light sources in theentire zone, a sharp change in the luminance level may occur at theboundaries between adjacent zones. In some embodiments, there may bemultiple luminance bands and corresponding transfer functions for lightsources in a zone, such that there may be a gradual change in theluminance level from one zone to an adjacent zone. As a result, thechange in the luminance level at the boundaries of a zone may be lessthan a threshold value that may be noticeable by the human eyes. Forexample, each of the different display zones may be associated withmultiple luminance bands and multiple discrete transfer functions forthe multiple luminance bands. Each of the luminance bands and thediscrete transfer functions may correspond to a different sub-zonewithin the corresponding zone. Adjacent sub-zones at the interfacebetween adjacent zones may have identical or nearly identical luminancebands and transfer functions. For example, a sub-zone in a region justbefore the first radius r₁ in the first zone A may have a transferfunction that is identical or nearly identical to a transfer functionfor a sub-zone just after the first radius r₁ in the second zone B.

In some embodiments, the gradient of luminance levels to avoid sharpchanges in luminance level between adjacent zones may be achieved byperforming an extrapolation based on the transfer function correspondingto the center (or another location) of a zone and the transfer functioncorresponding to the center (or another location) of an adjacent zone.The gradient of luminance levels may be selected such that thedifference between the luminance levels of light sources in adjacentzones is less than a threshold value and thus is imperceptible by thehuman eyes.

The display value referenced in FIGS. 12C and 12D may be a grayscalelevel or drive level for white (or gray) color. The display valuereferenced in FIGS. 12C and 12D may also be a drive level for lightsources in a color display in which each pixel includes three lightsources (e.g., three OLEDs or micro-LEDs) that are configured to emitred, green, and blue light, respectively, where the light sources foreach color may have a respective transfer function. For example, thedriver level may be within a range from 0 to 255 for red, green, or bluecolor when the display value of each color is represented by an 8-bitinteger.

The controller or the drive circuits (e.g., controller 1100) of adisplay may be configured to drive light sources within different zonesof the display with different voltages and/or currents based onpredetermined luminance bands (e.g., luminance ranges) and transferfunctions for the different zones, such that the light sources withinthe different zones of the display may emit light at different luminancelevels for the same display value. In some embodiments, the controlleror the drive circuits may be configured to drive groups of the lightsources within the display with different currents for a same displayvalue, such that each of the light sources within a group emits light atthe same luminance level, but light sources in different groups may emitlight at different luminance levels. The drive voltage or current foreach of the light sources within the display may be determined based on,for example, graph 1215 shown in FIG. 12D. In some examples, each lightsource may be an OLED or a micro-LED that can be controlledindividually.

FIG. 13 is a simplified flowchart 1300 illustrating an example of amethod for driving light sources in a display system according tocertain embodiments. The operations in flowchart 1300 may be performedby, for example, display electronics 122 or controller 1100 describedabove. Each light source in the display system may include an OLED or amicro-LED. At block 1310, a controller, such as controller 1100, maydetermine a maximum luminance location of a display based on a field ofview of an eye of a user of the display. In some embodiments,determining the maximum luminance location of the display may includetracking the eye of the user with respect to the display. The field ofview of the eye of the user may be determined based on the position ofthe eye of the user and/or a gaze direction of the eye of the user. Insome embodiments, the maximum luminance location may be at a center ofthe field of view of the eye of the user. In some embodiments, themaximum luminance location may be within a field of view of a fovea ofthe eye of the user.

At block 1320, the controller may drive a plurality of light sources inthe display based on locations of the plurality of light sources withrespect to the maximum luminance location of the display. Each lightsource of the plurality of light sources is driven by a respective drivecircuit to emit light. For a first light source and a second lightsource in the plurality of light sources and associated with a sameinput display value, the first light source may be driven to emit lightat a first luminance level higher than a second luminance level of thesecond light source that is farther from the maximum luminance locationthan the first light source. For example, the controller may, at block1322, drive the first light source based on the input display value anda first relationship between input display values and luminance levelsfor light sources in a first display zone of the display; and, at block1324, drive the second light source based on the input display value anda second relationship between input display values and luminance levelsfor light sources in a second display zone of the display. The luminancelevels for the light sources in the first display zone may becharacterized by a first range larger than a second range of theluminance levels for the light sources in the second display zone. Insome embodiments, a difference between the first luminance level and thesecond luminance level is less than a threshold value.

Embodiments disclosed herein may be used to implement components of anartificial reality system or may be implemented in conjunction with anartificial reality system. Artificial reality is a form of reality thathas been adjusted in some manner before presentation to a user, whichmay include, for example, a virtual reality, an augmented reality, amixed reality, a hybrid reality, or some combination and/or derivativesthereof. Artificial reality content may include completely generatedcontent or generated content combined with captured (e.g., real-world)content. The artificial reality content may include video, audio, hapticfeedback, or some combination thereof, and any of which may be presentedin a single channel or in multiple channels (such as stereo video thatproduces a three-dimensional effect to the viewer). Additionally, insome embodiments, artificial reality may also be associated withapplications, products, accessories, services, or some combinationthereof, that are used to, for example, create content in an artificialreality and/or are otherwise used in (e.g., perform activities in) anartificial reality. The artificial reality system that provides theartificial reality content may be implemented on various platforms,including an HMD connected to a host computer system, a standalone HMD,a mobile device or computing system, or any other hardware platformcapable of providing artificial reality content to one or more viewers.

FIG. 14 is a simplified block diagram of an example electronic system1400 of an example near-eye display (e.g., HMD device) for implementingsome of the examples disclosed herein. Electronic system 1400 may beused as the electronic system of an HMD device or other near-eyedisplays described above. In this example, electronic system 1400 mayinclude one or more processor(s) 1410 and a memory 1420. Processor(s)1410 may be configured to execute instructions for performing operationsat a plurality of components, and can be, for example, a general-purposeprocessor or microprocessor suitable for implementation within aportable electronic device. Processor(s) 1410 may be communicativelycoupled with a plurality of components within electronic system 1400. Torealize this communicative coupling, processor(s) 1410 may communicatewith the other illustrated components across a bus 1440. Bus 1440 may beany subsystem adapted to transfer data within electronic system 1400.Bus 1440 may include a plurality of computer buses and additionalcircuitry to transfer data.

Memory 1420 may be coupled to processor(s) 1410. In some embodiments,memory 1420 may offer both short-term and long-term storage and may bedivided into several units. Memory 1420 may be volatile, such as staticrandom-access memory (SRAM) and/or dynamic random-access memory (DRAM)and/or non-volatile, such as read-only memory (ROM), flash memory, andthe like. Furthermore, memory 1420 may include removable storagedevices, such as secure digital (SD) cards. Memory 1420 may providestorage of computer-readable instructions, data structures, programmodules, and other data for electronic system 1400. In some embodiments,memory 1420 may be distributed into different hardware modules. A set ofinstructions and/or code might be stored on memory 1420. Theinstructions might take the form of executable code that may beexecutable by electronic system 1400, and/or might take the form ofsource and/or installable code, which, upon compilation and/orinstallation on electronic system 1400 (e.g., using any of a variety ofgenerally available compilers, installation programs,compression/decompression utilities, etc.), may take the form ofexecutable code.

In some embodiments, memory 1420 may store a plurality of applicationmodules 1422 through 1424, which may include any number of applications.Examples of applications may include gaming applications, conferencingapplications, video playback applications, or other suitableapplications. The applications may include a depth sensing function oreye tracking function. Application modules 1422-1424 may includeparticular instructions to be executed by processor(s) 1410. In someembodiments, certain applications or parts of application modules1422-1424 may be executable by other hardware modules 1480. In certainembodiments, memory 1420 may additionally include secure memory, whichmay include additional security controls to prevent copying or otherunauthorized access to secure information.

In some embodiments, memory 1420 may include an operating system 1425loaded therein. Operating system 1425 may be operable to initiate theexecution of the instructions provided by application modules 1422-1424and/or manage other hardware modules 1480 as well as interfaces with awireless communication subsystem 1430 which may include one or morewireless transceivers. Operating system 1425 may be adapted to performother operations across the components of electronic system 1400including threading, resource management, data storage control and othersimilar functionality.

Wireless communication subsystem 1430 may include, for example, aninfrared communication device, a wireless communication device and/orchipset (such as a Bluetooth® device, an IEEE 802.11 device, a Wi-Fidevice, a WiMax device, cellular communication facilities, etc.), and/orsimilar communication interfaces. Electronic system 1400 may include oneor more antennas 1434 for wireless communication as part of wirelesscommunication subsystem 1430 or as a separate component coupled to anyportion of the system. Depending on desired functionality, wirelesscommunication subsystem 1430 may include separate transceivers tocommunicate with base transceiver stations and other wireless devicesand access points, which may include communicating with different datanetworks and/or network types, such as wireless wide-area networks(WWANs), wireless local area networks (WLANs), or wireless personal areanetworks (WPANs). A WWAN may be, for example, a WiMax (IEEE 802.16)network. A WLAN may be, for example, an IEEE 802.11x network. A WPAN maybe, for example, a Bluetooth network, an IEEE 802.15x, or some othertypes of network. The techniques described herein may also be used forany combination of WWAN, WLAN, and/or WPAN. Wireless communicationssubsystem 1430 may permit data to be exchanged with a network, othercomputer systems, and/or any other devices described herein. Wirelesscommunication subsystem 1430 may include a means for transmitting orreceiving data, such as identifiers of HMD devices, position data, ageographic map, a heat map, photos, or videos, using antenna(s) 1434 andwireless link(s) 1432. Wireless communication subsystem 1430,processor(s) 1410, and memory 1420 may together comprise at least a partof one or more of a means for performing some functions disclosedherein.

Embodiments of electronic system 1400 may also include one or moresensors 1490. Sensor(s) 1490 may include, for example, an image sensor,an accelerometer, a pressure sensor, a temperature sensor, a proximitysensor, a magnetometer, a gyroscope, an inertial sensor (e.g., a modulethat combines an accelerometer and a gyroscope), an ambient lightsensor, or any other similar module operable to provide sensory outputand/or receive sensory input, such as a depth sensor or a positionsensor. For example, in some implementations, sensor(s) 1490 may includeone or more inertial measurement units (IMUs) and/or one or moreposition sensors. An IMU may generate calibration data indicating anestimated position of the HMD device relative to an initial position ofthe HMD device, based on measurement signals received from one or moreof the position sensors. A position sensor may generate one or moremeasurement signals in response to motion of the HMD device. Examples ofthe position sensors may include, but are not limited to, one or moreaccelerometers, one or more gyroscopes, one or more magnetometers,another suitable type of sensor that detects motion, a type of sensorused for error correction of the IMU, or any combination thereof. Theposition sensors may be located external to the IMU, internal to theIMU, or any combination thereof. At least some sensors may use astructured light pattern for sensing.

Electronic system 1400 may include a display module 1460. Display module1460 may be a near-eye display, and may graphically present information,such as images, videos, and various instructions, from electronic system1400 to a user. Such information may be derived from one or moreapplication modules 1422-1424, virtual reality engine 1426, one or moreother hardware modules 1480, a combination thereof, or any othersuitable means for resolving graphical content for the user (e.g., byoperating system 1425). Display module 1460 may use LCD technology, LEDtechnology (including, for example, OLED, ILED, μ-LED, AMOLED, TOLED,etc.), light emitting polymer display (LPD) technology, or some otherdisplay technology.

Electronic system 1400 may include a user input/output module 1470. Userinput/output module 1470 may allow a user to send action requests toelectronic system 1400. An action request may be a request to perform aparticular action. For example, an action request may be to start or endan application or to perform a particular action within the application.User input/output module 1470 may include one or more input devices.Example input devices may include a touchscreen, a touch pad,microphone(s), button(s), dial(s), switch(es), a keyboard, a mouse, agame controller, or any other suitable device for receiving actionrequests and communicating the received action requests to electronicsystem 1400. In some embodiments, user input/output module 1470 mayprovide haptic feedback to the user in accordance with instructionsreceived from electronic system 1400. For example, the haptic feedbackmay be provided when an action request is received or has beenperformed.

Electronic system 1400 may include a camera 1450 that may be used totake photos or videos of a user, for example, for tracking the user'seye position. Camera 1450 may also be used to take photos or videos ofthe environment, for example, for VR, AR, or MR applications. Camera1450 may include, for example, a complementary metal-oxide-semiconductor(CMOS) image sensor with a few millions or tens of millions of pixels.In some implementations, camera 1450 may include two or more camerasthat may be used to capture 3-D images.

In some embodiments, electronic system 1400 may include a plurality ofother hardware modules 1480. Each of other hardware modules 1480 may bea physical module within electronic system 1400. While each of otherhardware modules 1480 may be permanently configured as a structure, someof other hardware modules 1480 may be temporarily configured to performspecific functions or temporarily activated. Examples of other hardwaremodules 1480 may include, for example, an audio output and/or inputmodule (e.g., a microphone or speaker), a near field communication (NFC)module, a rechargeable battery, a battery management system, awired/wireless battery charging system, etc. In some embodiments, one ormore functions of other hardware modules 1480 may be implemented insoftware.

In some embodiments, memory 1420 of electronic system 1400 may alsostore a virtual reality engine 1426. Virtual reality engine 1426 mayexecute applications within electronic system 1400 and receive positioninformation, acceleration information, velocity information, predictedfuture positions, or any combination thereof of the HMD device from thevarious sensors. In some embodiments, the information received byvirtual reality engine 1426 may be used for producing a signal (e.g.,display instructions) to display module 1460. For example, if thereceived information indicates that the user has looked to the left,virtual reality engine 1426 may generate content for the HMD device thatmirrors the user's movement in a virtual environment. Additionally,virtual reality engine 1426 may perform an action within an applicationin response to an action request received from user input/output module1470 and provide feedback to the user. The provided feedback may bevisual, audible, or haptic feedback. In some implementations,processor(s) 1410 may include one or more GPUs that may execute virtualreality engine 1426.

In various implementations, the above-described hardware and modules maybe implemented on a single device or on multiple devices that cancommunicate with one another using wired or wireless connections. Forexample, in some implementations, some components or modules, such asGPUs, virtual reality engine 1426, and applications (e.g., trackingapplication), may be implemented on a console separate from thehead-mounted display device. In some implementations, one console may beconnected to or support more than one HMD.

In alternative configurations, different and/or additional componentsmay be included in electronic system 1400. Similarly, functionality ofone or more of the components can be distributed among the components ina manner different from the manner described above. For example, in someembodiments, electronic system 1400 may be modified to include othersystem environments, such as an AR system environment and/or an MRenvironment.

The methods, systems, and devices discussed above are examples. Variousembodiments may omit, substitute, or add various procedures orcomponents as appropriate. For instance, in alternative configurations,the methods described may be performed in an order different from thatdescribed, and/or various stages may be added, omitted, and/or combined.Also, features described with respect to certain embodiments may becombined in various other embodiments. Different aspects and elements ofthe embodiments may be combined in a similar manner. Also, technologyevolves and, thus, many of the elements are examples that do not limitthe scope of the disclosure to those specific examples.

Specific details are given in the description to provide a thoroughunderstanding of the embodiments. However, embodiments may be practicedwithout these specific details. For example, well-known circuits,processes, systems, structures, and techniques have been shown withoutunnecessary detail in order to avoid obscuring the embodiments. Thisdescription provides example embodiments only, and is not intended tolimit the scope, applicability, or configuration of the invention.Rather, the preceding description of the embodiments will provide thoseskilled in the art with an enabling description for implementing variousembodiments. Various changes may be made in the function and arrangementof elements without departing from the spirit and scope of the presentdisclosure.

Also, some embodiments were described as processes depicted as flowdiagrams or block diagrams. Although each may describe the operations asa sequential process, many of the operations may be performed inparallel or concurrently. In addition, the order of the operations maybe rearranged. A process may have additional steps not included in thefigure. Furthermore, embodiments of the methods may be implemented byhardware, software, firmware, middleware, microcode, hardwaredescription languages, or any combination thereof. When implemented insoftware, firmware, middleware, or microcode, the program code or codesegments to perform the associated tasks may be stored in acomputer-readable medium such as a storage medium. Processors mayperform the associated tasks.

It will be apparent to those skilled in the art that substantialvariations may be made in accordance with specific requirements. Forexample, customized or special-purpose hardware might also be used,and/or particular elements might be implemented in hardware, software(including portable software, such as applets, etc.), or both. Further,connection to other computing devices such as network input/outputdevices may be employed.

With reference to the appended figures, components that can includememory can include non-transitory machine-readable media. The term“machine-readable medium” and “computer-readable medium” may refer toany storage medium that participates in providing data that causes amachine to operate in a specific fashion. In embodiments providedhereinabove, various machine-readable media might be involved inproviding instructions/code to processing units and/or other device(s)for execution. Additionally or alternatively, the machine-readable mediamight be used to store and/or carry such instructions/code. In manyimplementations, a computer-readable medium is a physical and/ortangible storage medium. Such a medium may take many forms, including,but not limited to, non-volatile media, volatile media, and transmissionmedia. Common forms of computer-readable media include, for example,magnetic and/or optical media such as compact disk (CD) or digitalversatile disk (DVD), punch cards, paper tape, any other physical mediumwith patterns of holes, a RAM, a programmable read-only memory (PROM),an erasable programmable read-only memory (EPROM), a FLASH-EPROM, anyother memory chip or cartridge, a carrier wave as described hereinafter,or any other medium from which a computer can read instructions and/orcode. A computer program product may include code and/ormachine-executable instructions that may represent a procedure, afunction, a subprogram, a program, a routine, an application (App), asubroutine, a module, a software package, a class, or any combination ofinstructions, data structures, or program statements.

Those of skill in the art will appreciate that information and signalsused to communicate the messages described herein may be representedusing any of a variety of different technologies and techniques. Forexample, data, instructions, commands, information, signals, bits,symbols, and chips that may be referenced throughout the abovedescription may be represented by voltages, currents, electromagneticwaves, magnetic fields or particles, optical fields or particles, or anycombination thereof.

Terms, “and” and “or” as used herein, may include a variety of meaningsthat are also expected to depend at least in part upon the context inwhich such terms are used. Typically, “or” if used to associate a list,such as A, B, or C, is intended to mean A, B, and C, here used in theinclusive sense, as well as A, B, or C, here used in the exclusivesense. In addition, the term “one or more” as used herein may be used todescribe any feature, structure, or characteristic in the singular ormay be used to describe some combination of features, structures, orcharacteristics. However, it should be noted that this is merely anillustrative example and claimed subject matter is not limited to thisexample. Furthermore, the term “at least one of” if used to associate alist, such as A, B, or C, can be interpreted to mean any combination ofA, B, and/or C, such as A, AB, AC, BC, AA, ABC, AAB, AABBCCC, etc.

Further, while certain embodiments have been described using aparticular combination of hardware and software, it should be recognizedthat other combinations of hardware and software are also possible.Certain embodiments may be implemented only in hardware, or only insoftware, or using combinations thereof. In one example, software may beimplemented with a computer program product containing computer programcode or instructions executable by one or more processors for performingany or all of the steps, operations, or processes described in thisdisclosure, where the computer program may be stored on a non-transitorycomputer readable medium. The various processes described herein can beimplemented on the same processor or different processors in anycombination.

Where devices, systems, components or modules are described as beingconfigured to perform certain operations or functions, suchconfiguration can be accomplished, for example, by designing electroniccircuits to perform the operation, by programming programmableelectronic circuits (such as microprocessors) to perform the operationsuch as by executing computer instructions or code, or processors orcores programmed to execute code or instructions stored on anon-transitory memory medium, or any combination thereof. Processes cancommunicate using a variety of techniques, including, but not limitedto, conventional techniques for inter-process communications, anddifferent pairs of processes may use different techniques, or the samepair of processes may use different techniques at different times.

The specification and drawings are, accordingly, to be regarded in anillustrative rather than a restrictive sense. It will, however, beevident that additions, subtractions, deletions, and other modificationsand changes may be made thereunto without departing from the broaderspirit and scope as set forth in the claims. Thus, although specificembodiments have been described, these are not intended to be limiting.Various modifications and equivalents are within the scope of thefollowing claims.

What is claimed is:
 1. A method comprising: determining a maximumluminance location of a display based on a field of view of an eye of auser of the display; and driving a plurality of light sources in thedisplay based on locations of the plurality of light sources withrespect to the maximum luminance location of the display, wherein: eachlight source of the plurality of light sources is driven by a respectivedrive circuit to emit light; and for a first light source and a secondlight source in the plurality of light sources and associated with asame input display value, the first light source is driven to emit lightat a first luminance level higher than a second luminance level of thesecond light source that is farther from the maximum luminance locationthan the first light source.
 2. The method of claim 1, wherein themaximum luminance location is at a center of the field of view of theeye of the user.
 3. The method of claim 1, wherein the maximum luminancelocation is within a field of view of a fovea of the eye of the user. 4.The method of claim 1, wherein determining the maximum luminancelocation of the display includes tracking a position of the eye of theuser with respect to the display.
 5. The method of claim 1, whereindriving the plurality of light sources comprises: driving the firstlight source based on the input display value and a first relationshipbetween input display values and luminance levels for light sources in afirst display zone of the display; and driving the second light sourcebased on the input display value and a second relationship between inputdisplay values and luminance levels for light sources in a seconddisplay zone of the display, wherein the luminance levels for the lightsources in the first display zone are characterized by a first rangelarger than a second range of the luminance levels for the light sourcesin the second display zone.
 6. The method of claim 1, wherein adifference between the first luminance level and the second luminancelevel is less than a threshold value.
 7. The method of claim 1, whereineach light source of the plurality of light sources includes an organiclight emitting diode (OLED) or a micro-light emitting diode (micro-LED).8. A system comprising: a display comprising a plurality of lightsources; and a display controller including a respective drive circuitfor each of the plurality of light sources, the display controllerconfigured to: select a maximum luminance location of the display basedon a field of view of an eye of a user of the system; and drive theplurality of light sources based on locations of the plurality of lightsources with respect to the maximum luminance location of the display,wherein, for a first light source and a second light source in theplurality of light sources and associated with a same input displayvalue, the display controller is configured to drive the first lightsource to emit light at a first luminance level higher than a secondluminance level of the second light source that is farther from themaximum luminance location than the first light source.
 9. The system ofclaim 8, wherein the maximum luminance location is in a field of view ofa fovea of the eye of the user.
 10. The system of claim 8, wherein themaximum luminance location is at a center of the field of view of theeye of the user.
 11. The system of claim 8, wherein the maximumluminance location is at a center of the display.
 12. The system ofclaim 8, wherein the display controller is configured to: drive thefirst light source based on the input display value and a firstrelationship between input display values and luminance levels for lightsources in a first display zone of the display; and drive the secondlight source based on the input display value and a second relationshipbetween input display values and luminance levels for light sources in asecond display zone of the display, wherein the luminance levels for thelight sources in the first display zone are characterized by a firstrange lager than a second range of the luminance levels for the lightsources in the second display zone.
 13. The system of claim 8, wherein adifference between the first luminance level and the second luminancelevel is less than a threshold value that is noticeable by the eye ofthe user.
 14. The system of claim 8, wherein the display controller isconfigured to drive each light source of the plurality of light sourcesbased upon a distance from the light source to the maximum luminancelocation.
 15. The system of claim 8, further comprising an eye-trackingsubsystem configured to: track a position of the eye of the user withrespect to the display; and determine a gaze direction or the field ofview of the eye of the user.
 16. The system of claim 8, wherein eachlight source of the plurality of light sources includes an organic lightemitting diode (OLED) or a micro-light emitting diode (micro-LED).
 17. Anon-transitory machine-readable storage medium including instructionsstored thereon, the instructions, when executed by one or moreprocessors, cause the one or more processors to perform operationsincluding: determining a maximum luminance location of a display basedon a field of view of an eye of a user of the display; and driving aplurality of light sources in the display based on locations of theplurality of light sources with respect to the maximum luminancelocation of the display, wherein: each light source of the plurality oflight sources is driven by a respective drive circuit to emit light; andfor a first light source and a second light source in the plurality oflight sources and associated with a same input display value, the firstlight source is driven to emit light at a first luminance level higherthan a second luminance level of the second light source that is fartherfrom the maximum luminance location than the first light source.
 18. Thenon-transitory machine-readable storage medium of claim 17, wherein themaximum luminance location is at a center of the field of view of theeye of the user.
 19. The non-transitory machine-readable storage mediumof claim 17, wherein determining the maximum luminance location of thedisplay includes tracking a position of the eye of the user with respectto the display.
 20. The non-transitory machine-readable storage mediumof claim 17, wherein driving the plurality of light sources comprises:driving the first light source based on the input display value and afirst relationship between input display values and luminance levels forlight sources in a first display zone of the display; and driving thesecond light source based on the input display value and a secondrelationship between input display values and luminance levels for lightsources in a second display zone of the display, wherein the luminancelevels for the light sources in the first display zone are characterizedby a first range larger than a second range of the luminance levels forthe light sources in the second display zone.